31st International Symposium on Ballistics
Application of Flash X-Ray Radiography System in Muzzle Image Diagnosis of Railgun
Because the X-ray can penetrate the flame and smoke in the railgun's muzzle to detect the armature situation, an X-ray digital imaging system is assembled for railgun muzzle diagnostics, which consists of Scandiflash 300kV flash X-ray system, PROSCAN 35 X-ray computer radiography (CR) imaging system and image processing software. The flash Xray system provides short and intense pulses of X-ray. The image plates are placed behind the armature, perpendicular to the x-ray beam axis. The X-ray digital imaging system can take 4 time sequence images of 1.4m within the muzzle of projectile. Observing these images, the experimental information about the trajectory, attitude and appearance of the armature can be obtained. And some important ballistic parameters, such as muzzle velocity and the ablation condition of armature also can be obtained via analyzing these images. The parameters can provide reliable experimental parameters for the mechanism of electromagnetic launch and designing the railgun launcher.
Modifications of the Closed Vessel Test Results Analysis Method
Some modifications of the closed vessel test results analysis method have been proposed. The first modification concerns the method of smoothing pressure records. It was shown that the Loess algorithm is very effective for smoothing very perturbed pressure records. The second modification consists in the shape function approximation method. The third modification concerns the method of determining the value of the exponent in the burning law. Two methods have been proposed. The first uses the geometric burning law. The second method is based on the physical burning law. It was shown that when the burning process of a propellant in the closed vessel obeys the geometric law, the two methods give close dependence of the burning rate on the pressure. However, when the burning process deviates from the geometric law, only the second method provides reliable results. The Loess algorithm and the shape function approximation method are described in the appendices.
Numerical Simulation of Drying Process of Multi-Perforated Stick Propellants
Drying is a complicated process which are involving simultaneous heat and mass transfer in the actual production of stick propellants. Inappropriate drying time and temperature may lead to poorer performance of cutting propellants and failure of propellant matrix shape. Numerical approaches are performed for understanding the drying process of stick propellants. In this paper, a software COMSOL, based on finite element, is used for investigating the drying rate and the concentration distribution of the solvent in the propellant matrix. The mesh, composed by 170000 quadrilateral elements, is created by the software on the physical field control condition. The solvent content of stick propellants is decreasing as time passes out that should be true physically. The numerical results indicate that the existent of the perforations has a little influence on the solvent distribution of stick propellants. The major advantage of this method is that the behavior of the entire drying process can be predicted well because the drying analysis of the propellant matrix are incorporated with the mass and energy transfer. It can provide theoretical guidance for the drying process and its parameters of stick propellants.
Thermal Decomposition of Rigid Polyurethane Foams/RDX Gun Propellants
Thermal decomposition of foamed propellant based on rigid polyurethane foams and 1,3,5- trinitro-1,3,5-triazinane (RDX) was studied by TG and DSC. The exothermal reaction kinetics was studied by differential scanning calorimetry (DSC) in no-isothermal conditions at different heating rates in atmosphere and high pressures. The results showed: With the increase of pressure, the peak temperature and the decomposition heat rises. Meanwhile, the decomposition curves presented secondary exothermic peaks under high pressures, resulting from autocatalysis and self-heating. The activation energy obtained by Kissinger and Ozawa methods is similar, and with the pressure increased, the activation energy deceased. The critical temperature of thermal explosion is lower than RDX.
Numerical Simulation of Gas Flow in Inner Perforation of Partially Cut Stick Propellants
The gas flow in the inner perforation of partially cut stick propellants is very complex and the gas flow parameters change constantly due to the existence of ordered incisions. The numerical simulation method can be conducive to further exploring the gas flow and its pressure and velocity distribution inside the inner perforation of stick propellants. Based on some assumptions, the inner perforation of stick propellants is a cylindrical channel with the ordered incisions, which can be simplified as a two-dimensional axisymmetric system. The calculation domain of the model is a rectangle which the width is 1 mm and length is 50 mm. The numerical results show that the existence of incisions can adjust pressure in the inner perforation of stick propellants well. A rapid change of pressure and velocity of the gas in the inner perforation was formed near the incisions. The gas can escape through the incisions in time, which is beneficial to decrease the pressure and mitigate the erosive burning inside inner perforations of stick propellants. The results of numerical simulation are not only helpful to explain how the incision of partially cut stick propellants can effectively mitigate erosive burning, but also provide a theoretical guidance for the production of partially cut stick propellants.
Recent Update on the Multi-Physical Model of Electromagnetic Railgun
This paper begins with a brief review of the development of computational codes on the multi-physical fields of electromagnetic railgun, followed by an introduction of recent updates in the modeling of structural dynamics. The multi-physical fields model was partly verified by experiments. The capacities of the computational code for the multi-physical fields were demonstrated by several examples. Some details of the launching process were illustrated, and the mechanisms of rail vibration, armature balloting motion, arc transition, rail gouging, and interface wear were discussed. The results show that the material nonlinearity plays a key role in modeling the structural dynamic behaviors.
Comparative Analysis of the Effects of Gunpowder and Plasma Ignition in Closed Vessel Tests
This paper presents the results of a comparative investigation into the effects of the ignition method on the ballistic properties of a single-base gun propellant, as determined via closed vessel tests. Conventional gunpowder ignition and plasma jet ignition methods were used. The influence of the ignition method on the dynamic vivacity is discussed. It is shown that this influence is significant in the first phase of the combustion process but in the second phase the dynamic vivacity plots converge. Regarding the burning law, close values of the exponent were obtained for the two ignition methods. The dynamic vivacity plots determined for plasma ignition reveal stronger dependence on the loading density than those determined for gunpowder ignition. The conclusion is that plasma ignition is not a solution to the problems inherent to the process of determining the ballistic properties of propellants, which burning process deviates from the geometric burning law.
Gradient Printing of Energetic Materials–First Results
This paper presents TNO’s first results on functional gradient printing of energetic materials. A multi-material 3D-printer with UV-curing capability was designed and constructed. This printer can handle highly viscous materials (> 200 Pa·s), allowing for solid loads above 70 wt%. Also included in the effort was the development of the software required to translate a multi-material propellant grain concept into printer command code, as well as the user control interface through which the printer can be controlled. For the first gradient printing demonstration, two materials were selected with a difference in burn rate large enough to lead to a significant performance increase when applied in a gun propellant grain. These materials were then used to print the first energetic propellant grain with a functional gradient. Finally, a continuous gradient was produced using co-extrusion of two (inert) material feeds, demonstrating the feasibility of this technique.
Effect of Particle Size of AP and Catalyst on the Thermal Decomposition of Ammonium Perchlorate
Analytical investigations on thermal decomposition behavior of course, fine and ultrafine ammonium perchlorate (AP) with and without catalyst were carried out by thermogravimetric and by differential thermal analysis.The low temperature decomposition (LTD) and high temperature decomposition (HTD) reactions and kinetic parameters for the two stages were computed using three non-mechanistic kinetic equations. With decrease in particle size of AP, the percentage mass loss in LTD decreases, but the overall reactivity increases. The variation of both activation energy (E) and pre-exponential factor (A) with particle size and catalyst impose difficulty in correlating the calculated E values with the observed enhancement in reaction rate due to decrease of particle size and catalyst. The E values calculated after normalizing the A values by kinetic compensation correction follows the expected trends. The catalytic activity of copper chromite was found higher than iron oxide in all fractions of AP decomposition behaviour.
Effect of Burn Rate Exponent Variation on Ballistic Performance of Gas Generator with High Burn Rate Propellant
For Gas Generator Internal Ballistics Prediction, Burn rate is important parameter as it determines the mass flow rate of the Gas Generator, which intern determines the canister pressure and ejection velocity of article launched from the canister by cold launch technique. The elemental law and empirical equation to determine the regression rate experimentally is ð‘Ÿ=ð‘Žð‘cð‘› , in which burn rate exponent ‘n’ is determined from the experimental measurements on actual propellants, different propellant formulations give different regression rate (Burn rate) verses pressure relationships. The burn rate exponent is independent of propellant grain temperature and describes the influence of chamber pressure on burning rate. High values of ‘n’ gives rapid change of burning rate with pressure, which means that even a small change in pressure will result in a substantial change in hot gas produces by Gas Generator. Since the high regression rate (25 mm/s) propellant is being used in the Gas Generator, chamber pressure varies from 10 to 27 MPa due to high mass flow rate requirement. It is important to note that this high regression rate propellant is particularly sensitive to pressure increase due to variation of burn rate exponent, particularly at high pressures. Mathematical coupling forms among pressure, Burt rate exponent (n) and regression rate, which leads to steep raise in chamber pressure after certain threshold pressure, which depends on propellant composition. This paper attempts to study and present the evaluation of burn rate index variation over pressure range 3 to 23 MPa and corresponding effect on ballistic performance of Gas Generator with high burn rate multi perforated propellant grain, which gives continues progressive mass flow rate.
A Novel Experimental Method to Measure Instantaneous Pressure Inside a Power Cartridge Using Velocity Test Rig and Projectile Velocity by Doppler Radar
The present article explains about the novel experimental method to measure the instantaneous pressure generated by propellant burning inside the cartridge case. The instantaneous pressure was evaluated with the help of data acquisition system in a specially designed and fabricated test rig named as velocity test rig (VTR). Doppler RADAR (radio detection and ranging) is used to measure the velocity of nylon projectile. A novel method or technique was devised to measure the instantaneous pressure inside the cartridge for launching such projectile. An experimental test set-up was fabricated to measure the propellant gas pressure in a VTR. The maximum projectile velocities for NGB 051 propellants and spherical ball powder were evaluated experimentally as 420.13 m/s and 384.23 m/s respectively. The maximum pressures for NGB 051 and spherical ball powder propellants were evaluated as 63.2 MPa and 52.18 MPa respectively. The standard deviation between the experimental values for the projectile velocity is 5.49 for NGB 051 whereas it was 12.53 for spherical ball powder propellant.
Internal Ballistics Studies on Compensation of Charge Temperature Effect for Large Caliber Gun System
The main aspiration of gun system is to propel projectile at desired range with high consistency and accuracy. Internal Ballistics (IB) plays a very vital role during design and development of gun systems. Initial temperature of charge system significantly affects gun IB performance. It is not always possible to conduct all gun firings at particular temperature conditions. Design of a temperature invariant charge system for large caliber guns is an important area of research in recent times. In this paper, a method is suggested for compensation of charge temperature effect on IB performance using Combustible Cartridge Case (CCC) physical parameters. A multivariate constrained optimization problem is defined for compensation of initial charge temperature effect on IB performance. The simulation results of this method show that the charge system can be converted into temperature independent by altering CCC physical parameters.
Gun Barrel Erosion Analysis Using a Coordinate Measuring Machine (CMM): Experimental and Statistic Study
This paper focuses on the development of an analytical model to predict the engraving pressure evolution and the chamber volume in terms of the inner barrel profile in different weapon life stages. The test barrel “12.7x99mm NATOâ€ is considered. First, a coordinate measuring machine (CMM) with a contact scanning probe is used to measure the inner dimension of the barrel in its different life stages. The CMM parameters; such us (i) the measuring force, (ii) the measured points, (iii) the scanning velocity; are investigated. In order to ensure minimum measurement incertitude, a statistical analysis is adopted to select the reliable CMM parameters combination. Second, piezoelectric sensors with a special doppler radar are considered to measure the (i) pressure, (ii) bullet velocity and, (iii) engraving pressure in the test barrel. Thus, based on analytical theories, a predictive algorithm is elaborated to match the inner barrel profile to the engraving pressure.
Design and Geometric Optimization of Solid Propellant Grain for Large Motors
In solid propellant grain, the burning surface area changes during motor operation and at each point its regression is in the direction of normal to the surface. The relationship between burning surface and web distance burned depends on the geometric shape and size of grain. The rate of propellant burnt is a factor of burning surface area. Thus the main focus is to design and optimize the grain shape and to obtain near constant values for thrust-time graph dependent parameters are burning surface area, L/D ratio, web thickness, burn rate. Finocyl grain(“fin in cylinderâ€) is selected for the studies as it is a 3D geometric configuration usually are complicated in terms of geometric analysis, it burns in both radial and longitudinal directions. A solid model of the grain is developed using 3D software. Therefore depending on the boundaries, fin geometries maybe varied to obtain desired results.
Thermal-Flow Coupling Simulation Analysis of Spiral Channel Water Cooled Radiator for High Power Thyristor
High power thyristor is the core switching device of pulse power source, which is an important component of electromagnetic launch (EML). So the reliability of high power thyristor directly affects the safe and reliable operation of EML. Semiconductor theoretical and experimental studies show that the electrical characteristics of thyristor are directly related to the change of junction temperature. In this paper, a spiral flow channel water-cooled radiator applied to cooling thyristor is analyzed to study its flow and thermal diffusion characteristics. And, its performance under different inlet flow rate, inlet temperature and heating power are compared. The results show that countercurrent design of adjacent channel is effective to maintain the uniformity of temperature distribution; and compared with inlet temperature or heating power, inlet flow rate has a greater impact on the performance of the radiator. Key words: EML, Pulse power supply, High power thyristor, Water cooled radiator, Spiral-Channel, Thermal-flow coupling simulation
Design Optimization for a Launching System with Novel Structure
A launching system with novel structure using optimization method is investigated to improve the muzzle velocity of guns in this article. This system has two tandem chambers of which the front one is ignited first and the other is ignited after a while. The launching process of this novel system is modelled to discover the interior ballistic performance of this novel launching system. In order to obtain the optimal loading conditions, an optimization model combined with the combustion model is established. In this research, the optimization model is applied to the novel launching system and conventional launching system, and compared with the original scheme. Both optimal schemes can achieve higher muzzle velocity, while the novel method could improve by 24.6% and the conventional method could improve by only 15.2%. It means that this novel launch system could improve the interior ballistics performance significantly and it still has considerable potential to be ameliorated. This paper is an extended abstract of a paper published in Defence Technology in 2019.
Calculation of Axial Magnetic Force of Solenoid Inductor Made of Coil with Rectangular Cross-Section
With the development of the electromagnetic launch technology, the calculation of magnetic forces is a subject of great importance. In this paper, we present analytic-numerical expression for the calculation of the axial magnetic force of solenoid inductor made of coil with rectangular cross-section, a two-dimensional model and a three-dimensional model was established and the finite element method was utilized to simulate the problem. Three cases are calculated by the above three methods. The results showed that the coil tends to close from both ends to the middle, and the outermost coil is subjected to the greatest electromagnetic force. Results obtained by the three approaches are in excellent agreement. Key words: Pulsed power supply, solenoid inductor, Axial magnetic force, FEM, Analytic-numerical
A Prediction Method for the Performance of a Low-recoil Gun with Front Nozzle
With the increasing muzzle velocity of guns, heavier mount is required to absorb the recoil during firing cycle. One of the greatest challenges in the design of a gun is to balance the muzzle velocity and the recoil, especially for guns on aircrafts and deployable vehicles. To resolve the conflict between gun power and maneuvering characteristics, lots of new low-recoil weapons and devices have been developed in recent years. A concept of rarefaction wave gun (RAVEN) was proposed by Dr. Kathe to meet the demand above. The RAVEN is based on rarefaction wave theory and has a similar structure to the recoilless gun. It can significantly reduce the weapon recoil and the heat in barrel, while minimally reducing the projectile velocity. The main principle of the RAVEN is that the rarefaction wave will not reach the projectile base until the muzzle by delaying the venting time of an expansion nozzle at the breech. Studies over the past two decades have provided important results on the RAVEN by experiments and theories. Recently, investigators have examined the effects of the open time and the positions of vents for the RAVEN. The performances of low-recoil guns such as muzzle velocity and recoil are very corresponding to both effects above, particularly for the RAVEN with front nozzle. The purpose of this paper is to provide an engineering method for predicting the performance of a low-recoil gun with front nozzle. Numerical simulations in the RAVEN with front nozzle were carried out by using the transient two-dimensional two-fluid theory. The propellant combustion, interphase drag, intergranular stress, and heat transfer between two phases were considered in all regions of the RAVEN with front nozzle. To reduce the computational cost and improve the simulation accuracy, the arbitrary Lagrangian-Eulerian approach was used to describe the motions of the projectile. And the second-order finite volume method was implemented efficiently to describe both gas and solid phases. The main conclusions of the study are as follows: (1) The simulation method was validated by a commonly used the AGARD gun. Comparisons of the predicted results of the AGARD gun by our code and other different codes in references demonstrate the accuracy and reliability of our present numerical method. (2) Based on the condition of the AGARD gun, a RAVEN with front nozzle was proposed and numerical simulations were provided to describe and understand the physical phenomenon of the interior ballistic process in the RAVEN with front nozzle. (3) The lower muzzle velocity and the lower recoil impulse are formed by shorter vent opening time. The rarefaction wave will reach the projectile base faster. The shorter distance between vent location and breech can increase the propagation length of the rarefaction wave. The muzzle velocity will increase and the recoil impulse will decrease.
Ultrasonic Cleaning of Weapon Components: State of the Art Technology
Life of any mechanical components depends upon the way of its utility and maintenance apart from the design and material aspect. Weapon/gun components are subjected to deposition of various by products of propellant burning during firing. Proof ranges are engaged for firing with heavy load, hence thorough cleaning of weapon components especially cavities, holes and recesses manually, is time consuming as well inefficient. Ultrasonic cleaning is a state of art technology and can be used for high quality cleaning of the weapon components with less time. In this paper some of the components of high calibre gun which are subjects to deposition of high contamination of propellant by products are cleaned by using ultrasonic cleaning machine. Different frequency and chemicals are used for the experiments and the best cleaning result has been identified. The maintainability and enhancement of weapon components life as well as reduction of its malfunction during firing observed.
Study on Properties of High-Nitrogen Single-Base Propellant Prepared from a Solvent Containing N-Butylacetate
In order to improve the mechanical properties of single-base propellant with high nitrogen content, 3% by weight of n-butyl acetate was added as an auxiliary solvent to the alcohol ketone mixed solvent to plasticize the high-nitrogen nitrocellulose in the propellant preparation. The test results of mechanical properties and combustion performance showed that the addition of n-butyl acetate significantly improved the mechanical properties of highnitrogen single-base propellant, but reduced some energy. Therefore, 3%wt of RDX was then added to compensate for this energy loss. The test results showed that the propellant finally obtained maintained its energy, and its impact strength at -40℃ was increased by 10.29% compared with the original sample.
Influences of Structural Parameters on Interior Ballistics Based on an Orthogonal Test Method
The influences of multiple structural parameters on interior ballistics were investigated by using an orthogonal test method. A coupled lumped parameter model was utilized to predict the propellant combustion, and a dynamic finite element method was applied to approximate the mechanical interactions between the projectile and the barrel. In order to reduce the research costs, orthogonal tests were designed to investigate the comprehensive effects of the parameters. According to statistical analysis, the important order of the structural parameters on the launching process was obtained. The results indicate that the influences caused by the width of the rotating band stand out among the studied parameters. This is an extended abstract of a paper published in Defence Technology, 2019.
Three-Dimensional Numerical Fluid Flow Simulation of the Interior and Transitional Ballistics Process
We report on the realization of a numerical tool to simulate the three-dimensional fluid flow associated with the interior ballistics problem of propellant based weapon systems. The model is based on a two-phase approach, in which the gaseous and the solid phase, representing the propellant bed, are assumed to be a homogeneously stirred mixture. The ignition and the combustion of the propellant grains are taken into account via heat and mass transfer, respectively, between the two phases. To numerically solve the governing set of equations, a Godunov scheme based on an approximate Riemann solver is applied. Interior ballistics simulations on a 60 mm weapon and experimental findings are compared and it is shown that the presented model, in principle, is also able to predict the muzzle flash after the projectile left the barrel
Data Management and Simulation of Pulse Power Supply Experiment
It is very important to manage mass experiment information and data efficiently in electromagnetic launch experiment, especially for large-scale pulse power supply (PPS), which has hundreds of power supply modules. Managing the device parameters, usage information and malfunction of the power supply module will help to plan the usage of the pulse power supply reasonably and prolong theirs service life. For this purpose, a special database management platform for PPS experiment is designed and developed. C# programming language is adopted to design a friendly man-machine interactive interface, and SQL Server software is used to establish and manage the database. The experiment management platform includes the functions of PPS management, experiment task management, experiment resource management, fault information management and simulation of PPS in electromagnetic launch experiment. It plays an important guiding role in maintaining and managing experiment data and assisting decision-making of experiment schemes.
Numerical Simulation of Transient Temperature Field and Thermal Stress in the Electromagnetic Railgun
In the process of electromagnetic railgun launch, the rapid temperature rise and thermal stress caused by heat accumulation have a serious impact on the continuous launch. Based on the analysis of the thermal load of the rail, a thermal load calculation model is established. Under the given parameters, the finite element software ANSYS Workbench is used to simulate the temperature field and thermal stress of the rectangular section rail under continuous launch. The simulation results show that the maximum temperature and thermal stress are at the initial position of the armature. During the four consecutive launches, the temperature fluctuates greatly and the maximum temperature increases gradually after each launch. The thermal stress also fluctuates greatly with the temperature. When the peak stress exceeds the yield limit, the plastic deformation occurs.
Numerical Research on the In-Bore Process of Rifle Bullet
In order to analysis the dynamic response of bullet and barrel during the in-bore process, bullet base pressure was calculated by interior ballistic theory, and numerical model of bullet in-bore process was established，the numerical model was validated by experimental results, which include muzzle velocity, spin velocity, width and depth of engraved bullet vestige, the maximum difference between the numerical and experimental results is 5.88%. The engraving process and engraved vestige on bullet, the changing of stress in bullet and barrel, and also the changing of temperature in bullet jacket were calculated, the study indicated that in engraving process, the maximum plastic strain in bullet engraved vestige is at right, and the maximum von-mise stress in rifling is at left, the left of rifling produced major contribution of the spin motion. The internal energy of jacket increased due to plastic deformation and friction at engraving process, which is 79.8% versus all internal energy increased, the other process is 20.2% and originates in friction mainly. After in-bore process, at bullet engraved vestige, the maximum temperature changing is reach to 235K, and the changing at other region is about 40K.
Numerical Simulation on the Pressure Wave in a 30MM Electrothermal-Chemical Gun with the Discharge Rod Plasma Generator
In this paper, an axisymmetric two-dimensional interior ballistics model of the solid propellant ETC gun (2D-IB-SPETCG) is used to simulate the 30mm ETC launch. The 2D-IB-SPETCG model includes: pulse forming network (PFN) discharge model [11, 12], DRPG model [13, 14] and 2D two-phase flow model [14, 15]. Depending on simulation results, the electric energy ratio and discharge timing sequences are used to analyze the influence of electric parameters (input electric power, discharging timing sequence) and charging parameters (loading density, propellant web thickness) on the pressure wave. In the ETC launch, the internal ballistic process can be influenced by both the input electric energy of the DRPG and the propellant chemical energy. The electric energy ratio, ηe, is the ratio of the input electric energy to the propellant chemical energy.
Numerical Simulation of Flow of Pyrotechnic Igniter Gases Inside Inert Solid Rocket Motor
A numerical model is developed to simulate the flow of gases produced due to pyrotechnic igniter inside an inert solid rocket motor chamber. Mass and energy generated by the combustion of pyrotechnic charge is released inside the free volume of igniter canister. The mass generation rate is calculated using pseudo-average-burn rate approach. The energy release rate is computed by obtaining the product of mass generated and calorific value of the charge. Commercially available CFD solver Fluent is utilized for modeling and a 3- dimensional, transient, compressible flow numerical model is developed. The k-ω turbulence model is used for turbulence modeling. The flow is computed for entire duration of the burning of charge and contours for variation of pressure, temperature and velocity inside the inert rocket motor are obtained. The model validation is carried by comparison of predicted and experimental pressure-time profile for Gunpowder composition and an excellent match is obtained.
Interior Ballistic Model with Variable Burn Rate Coefficients for Gun Propulsion System
A lumped parameter model has been formulated. Model has been programmed in MATLAB. Different propulsion system parameters like propellant, cartridge case, igniter, projectile and gun system are input to the program and projectile velocity and chamber pressure distribution are the major outputs. The model is validated with 105mm howitzer gun firing data from literature. The model, only after incorporating variable burn rate coefficients with pressure, has been tried with 120mm tank gun of HEMRL firing data with reasonable agreement
Analysis of a Novel Double Funnel Port Solid Rocket Propellant Grain Configuration for Achieving Improved Neutrality
In the present paper a double funnel port grain configuration is studied in detail. The neutrality of the grain configuration is compared with the neutrality of a single funnel port grain configuration. After optimization of double funnel port grain dimensions to achieve maximum neutrality, the predicted pressure–time profile of realized grain is compared with the achieved pressure-time profile from rocket motor static testing. A close match was obtained between the two profiles. Thus, double funnel port grain configuration is established which can be utilized for estimating burning rate of propellant compositions at any desired pressure with good neutrality.
Study of In-Bore Parameters of Armament Systems Using Doppler Radars
Performance evaluation of artillery gun system is carried out during the dynamic firing of armament stores. The recording of different ballistics parameters during dynamic firing plays an important role in assessment of armament stores. For characterization of internal ballistics of a gun and propellant, the velocity-time profile of the projectile and associated chamber pressure inside the barrel are two of the most crucial parameters. This paper presents details of measurement of in-bore velocity-time profile using Doppler radar systems. From the velocity time profile, acceleration-time profile has been obtained and subsequently base pressure and breech pressure time profiles have been calculated. The paper also deals with the effect of charge mass decay profile with time during combustion of propellant on computation of breech pressure-time profile. The average error observed between measured peak breech pressure from piezoelectric transducer and computed peak breech pressure from in-bore radar data is of the order of 2.3%.
Effect and Study of Supersonic Plume Impingement on Axis Symmetric Jet Deflector by Simulation
Missile launcher is being provided with Jet Deflector (JD) for protecting Launcher from hot plume of missile and diverting the plume away from launcher and preventing debris and gravels hitting launcher. Design of JD is required to be carried out by keeping extreme condition of direct plume impingement at high temperature and velocity. The JD surface is coated with heat resistant coating. Hence, there is a need to estimate thermal load and erosion rate on JD. The thickness of coating over JD is important to understand the number of missile firing that can be done on same location of JD. Simulations were carried out to estimate heat flux on JD surface and to estimate surface erosion. Simulation will reduce the cost incurred for testing of missile over JD. Maximum cold wall heat flux obtained by simulation is 44MW/m2 and erosion depth is 7.1 mm and in experimental is 6.5 mm.
Peak Pressure Variation with Grain Fracture: Using a Lumped Model for Projectile Energizing with Seven Perforation Grain
Propellant grain geometry plays a critical role in pressure space behaviours in interior ballistics which are important for operational safety of gun barrel designs. This geometry leads to a burning surface which is tractable to mathematical models only if the grains do not fracture. Complex high fidelity models for situations when grains fracture require significant computational effort. We propose to use instead the conventional lumped model with certain normative assumptions about grain fracture. We demonstrate that with seven perforation grains of two different lengths having different loading mass fractions to mimic fracturing, we can inform design insights concerning peak pressure variation. In particular, our results suggest that hole radius and outer radius could be optimized to provide minimum peak pressure variation on account of grain fracture.
Application of 5-Aminotetrazole In GAP/AN Based Propellant
The desire for the minimum signature property, e.g. less smoke or flame of gas plume, has become stronger in the solid rocket propellant development. 5-aminotetrazole(5-AT) and GAP/AN-based propellant were chosen as the filler component the based formulation respectively to obtain a novel minimum signature propellant. The propellant containing 5- aminotetrazole(5-AT) was prepared by flow casting technology to explore effect of 5-AT on propellants. Mechanical properties of propellant containing 5-AT were characterized by tensile test, burning rates were measured by the method of target lines. Results show that, the breaking elongation of propellant containing 5-AT increases ，but the tensile strength decreases by 57.7%. Compared with GAP/AN based propellant, the burning rate pressure exponent for propellant significantly decreases by 0.2 when the content of 5-AT is 10%ï¼Œ while burning rate increases by 15.3% at pressure of 9MPa.
Experimental Investigation of Initial Pressure Rise with Igniter Charge Mass in Single Grain Rocket Motor
In the present research work, the effect of the igniter charge mass on the initial pressure rise in single grain solid propellant rocket motor is investigated experimentally. The igniter in the rocket motor is used to ignite propellant in rocket motor. Experiments are done with varying igniter charge mass by approximately ±15% of the calculated igniter charge mass value i.e. ~35g. Maximum pressure noted at 35g calculated igniter charge mass is 8.5632 MPa. Various experiments with 25g, 30g, 40g and 45g of igniter charge mass is carried out to study the effect of igniter charge mass on maximum pressure in rocket motor keeping all other parameters i.e. nozzle throat diameter, nozzle end grid, head end grid etc. are kept same. For each igniter charge mass two static tests were conducted. As igniter charge mass is increased from 25g to 45g ignition transient pressure increased from 2.9 MPa to 5.65 MPa, by optimizing the igniter charge mass the initial pressure can be kept within required range of MEOP (Maximum Expected Operating Pressure) for safe working of rocket motor.
Empirical Co-Relation Between Burn Rate and Pressure Index of Spherical Gun Propellant in Closed Bomb
In this research paper, empirical relation between burn rate and pressure index of spherical gun propellant was carried out in the closed bomb. This is double base propellant and used in power cartridge to destroy the suspicious unattended objects. The novelty in this research is that, the author proposed a novel empirical relation among force constant, burning rate coefficient, pressure index and peak pressure. Ballistics properties like burning rate of propellant is depend upon on its shape and size (configuration), chemical composition, temperature, loading density and pressure. The major outcome of this research study has direct relevance for the performance prediction of propellant in the form of powder related to dynamic firings. The peak pressure of the propellant is 235.04 MPa, the rise time 1.95 ms, burn rate coefficient 0.073, pressure index 1.29, flame temperature 2680 0K and force constant 953.2 J/g were obtained during experiment. The burning rate for the spherical gun propellant is experimentally expressed as 1.29
Overcoming Erroneous Erosion of Electrically Launched Projectiles in Alegra Simulations
Hydrocode simulations were utilized to directly improve and guide design of an electrothermal research gun capable of firing small projectiles (0.25 g) at hypervelocity. The launch system uses an electrical arc and vaporization from a pointed copper anode with voltages up to 20 kV to produce a rapidly expanding gas as a propellant. The simulations were performed using ALEGRA with barrel expansion, projectile erosion, and velocity profiles as validation benchmarks. Guidance resulting from these benchmarked simulations led to projectile velocity gains of 30%. While the initial simulations reproduced and predicted the velocity profiles extremely well, significant erosion of the projectile occurred in the simulations that was not observed in the experiments. This was a direct result of Eulerian “weldingâ€ at the projectile/barrel interface. Several modifications to the simulations were implemented in this study to maintain the success observed in earlier velocity predictions while preserving projectile integrity to overcome erroneous erosion issues.
Experimental-Numerical Study of the Pressure & Projectile Velocity Measurement and Its Validation for Water Disruptor Application
Various experiments were performed on water disruptor to measure the velocity of water and projectile. In these experiments, double base propellants having different physical and chemical properties were utilized to drive the projectile. This projectile was made up of nylon material. Measurement of projectile velocity is significant parameter for disruptor in neutralizing IEDs. An attempt has been made to develop a mathematical model for processes taking place inside the water jet disruptor using internal ballistics model. A code has been developed based on the mathematical model and simulated for various input parameters. The validation of the code has been done by comparing the results with experimental firing. A parametric analysis is carried by varying barrel length of the disruptor, propellant type and projectile mass.
Implementation of a Gumbel Distribution Function in Interior Ballistic Calculations for Deterred Propellants
Based on the available bibliography three types of deterrent concentration profiles were identified. The cumulative distribution function of Gumbel distribution has the ability to reproduce all identified deterrent concentration variation profiles. The relationships between the ballistics characteristics and deterrent concentration can be expressed using the Gumbel function combined with a polynomial function. In order to deal with variability of mean values of burned propellant characteristics the interior ballistic specific equations should by modified accordingly. Based on available experimental data and the calculated variable ballistic characteristics the developed 0D model and the proposed functions are validated.
Preliminary Numerical and Experimental Investigations of 9 MM Pistol Bullet and Barrel Interaction
The paper presents results of numerical modeling of interaction between projectile and 9 mm pistol barrel. During the investigations, numerical results in quasi-static and dynamic conditions were obtained. Simulations in the first case allowed for validation of the model using the direct comparison of the theoretical results with resistant force courses obtained applying the experimental stand. The mechanical properties of projectile jacket were described based on the bilinear and Johnson – Cook model. For the dynamic case considerable differences between obtained results and results provided by simplified relationships proposed by Serebryakov were observed (over one order of magnitude). These discrepancies can be an effect of neglecting engraving process in the simplified approach. Applied approach to modeling the interaction between the bullet and the barrel, allows for implementation of obtained results in modeling of interior ballistics phenomena.
Preliminary Application Correctness Assessment of Physical Burning Law in Interior Ballistics Phenomena Modeling in Small-Caliber Guns
The paper presents the results of application correctness assessment of a physical burning law in theoretical interior ballistics phenomena modeling. Using the proposed lumped-parameters thermodynamic interior ballistics model, ballistic curves were obtained. In order to validate the used theoretical approach, experimental tests were conducted. Pressure courses, muzzle velocity and temperature courses of the barrel surface were measured and compared with the modeling results. The results obtained with the use of the geometrical burning law model showed a better agreement with the experiment than the results obtained with the physical burning law in which the dynamic vivacity function was estimated using closed vessel tests. The possible reason of this effect is the dependence of the dynamic vivacity function on the loading density, which is confirmed in the literature.
A Method to Add High Speed Sliding Contact Boundary Conditions into Moving Electromagnetic Field by Lagrange Multiplier Method
In the simulation of electromagnetic field in transient motion of electromagnetic railgun, we can use A, Φ-A method combining with Lagrange moving coordinate system method to calculate moving electromagnetic field. However, there will be accumulated errors on the high speed sliding contact surface by moving coordinate system method. And the high speed sliding contact boundary conditions should be applied to the electromagnetic field eliminate the errors. In the FEM(finite element model), apply the high speed sliding contact boundary conditions is complex. So we using the Lagrange multiplier method to add high speed sliding contact boundary conditions into FEM, that the large sparse matrix is easier to compute. The result of electromagnetic field, current density and electromagnetic have good characteristics of moving electromagnetic field. It shows that the calculation model in this paper has high accuracy.
An Experimental Method for Evaluating the Effectiveness of the Flame Inhibitor
In order to test the effect of flame inhibitor on the secondary flame of propellant gas accurately and conveniently, and study the effect of flame inhibitor on the muzzle flame, an experimental method for evaluating the effectiveness of the flame inhibitor is designed with applying the flame simulator, high speed video camera and Pro Plus Image software. The duration time of flame, maximum flame area, total area of flame and q value of five kinds of charges containing flame inhibitor (TEGDN propellant with 0 wt% KNO3, 0.3 wt% KNO3, 1 wt% KNO3 in formulation or added bag with 1 wt% KNO3, 4 wt% KNO3) were studied through the designed method. It is showed that the TEGDN propellant contains 1wt% KNO3 in formulation had the best test result. The experimental results are consistent with the actual results of the interior ballistic firing, which shows that the method is feasible.
Erosion of Different Propellants on the Cobalt-Based Alloy Coating for Gun Barrel
The cobalt-based coating was deposited on the surface of the PCrNi3MoVA gun steel via plasma transferred arc technology, and the coating samples were subjected to 30 accelerated erosion cycles in a modified pressure-vented vessel using two kinds of propellants of different particle sizes and detonation temperatures with the purpose of determining the erosion resistance of the coating, in order to explore the application of cobalt-based alloys in large-caliber barrel weapons. The results show that the two types of propellants have obvious differences in the degree of coating erosion due to different burning speeds and detonation temperatures.
Research Progress on Application of Refractory Metals and Superalloys in Gun Barrels
With the continuous improvement of the performance of barrel weapons, the requirement for the erosion resistance of the gun barrel material is getting higher and higher. Therefore, research on the new erosion resistant material and its preparation process for gun barrel has become an important research direction of barrel weapons. Refractory metals and superalloys have high melting points and excellent high temperature properties such as mechanical properties, wear resistance, corrosion resistance, etc. Recently, with refractory metals and superalloys becoming a major research direction of materials, their application for barrel weapons has gradually become a research hotspot. The performance requirements of refractory metals and superalloys in gun tube applications are summarized in detail. Meanwhile the research progress of their performance and applications in recent years is reviewed. On this basis, the progress of the research group focusing on the application of superalloys for gun barrels is mainly reported. It also pointed out the challenges that need to be faced in the protection of gun barrels by using refractory metals and superalloys, and prospects for future development.
Blow-by Erosion Model for the Saddle-Type Degradation of High Pressure Gun Bore
The erosion of high-pressure gun is different from that of ordinary gun bore. The degradation curve of the gun bore surface shapes like a unique saddle because of the two erosion peaks occurring. This particular erosion situation cannot be well explained using traditional heat transfer model and bore-cracking model. Therefore, a “blow-by erosionâ€ model for the explanation of this saddle-type degradation has been developed based on the internal ballistic model during the launch of the high-pressure gun combined with the “shot leakageâ€ phenomenon in gun bore, which can well explain the appearance of the second erosion peak on the high pressure gun bore surface. The theoretical calculation position is well consistent with the actual test results. Moreover, the model can also be used to assist in analyzing the surface degradation of other barrel weapons.
Evaluation of Internal Ballistics Properties of Naturally Aged Solid Propellant Rocket Motor
The naturally aged solid rocket motor is static tested for internal ballistics performance evaluation thus estimating service life. The motor propellant weight is 800 kg and composition is AP/Al/HTPB. After 10 years, propellant samples were cut and taken from motor port region, and test coupons were made from samples; and mechanical properties were evaluated, while ballistic properties determined from static test firing. The mechanical properties test results showed that decrease in tensile strength and elongation and increase in Young’s modulus. The margin of safety on propellant is reduced to 0.3 from 1.0. The aged motor performance was evaluated by full-scale static test firing. The test results show that reduction in ballistics and mechanical properties are due to ageing but no reduction is observed in propellant energy i.e., Isp(delivered). The aged solid rocket motor performed close to lower mission bound and within acceptable limit and the determined motor service life is 10 years.
Coating Processes Towards Selective Laser Sintering of Energetic Materials
Additive manufacturing (AM) technologies are maturing and allowing effective manufacturing of components, including those of energetic material devices. On the other hand, technology advances in AM may also enable more complex fabrication of improvised explosive devices that are hard to detect. Stakeholders within the defence research and development sector need to comprehend this potential threat and strive to develop counter solutions. This work aims to contribute to the safe methodology for AM of energetic materials. Coating formulation processes were investigated and evaluated to find a suitable method that may enable selective laser sintering (SLS) as the safe method for fabrication of high explosive (HE) compositions. For safety and convenience reasons, the concept demonstration was conducted using inert explosive simulants with properties quasi-similar to the real HE. One of the coating processes for simulant RDX-based microparticles by means of a polymer is reported. These processes were evaluated for uniformity of coating the HE inert simulant particles with binder materials to facilitate the SLS as the adequate binding and fabrication method. The suspension process appears to be suitable for the SLS of polymer coated HE mocks and potential formulation methods for active HE composites. The processes investigated pave the way toward safe SLS of the active HE compositions and may open avenues for further research and development of munitions of the future. This is an extended abstract of a paper published in Defence Technology (2019), DOI:https://doi.org/10.1016/j.dt.2019.05.013.
Research for Diffusion of the Polymer Deterrent in the Gun Propellant
In this paper, the polymer deterrent NA (the polyester which is synthesized by condensation of binary acid and dihydric alcohol) is synthesized and its structures are characterized by proton magnetic resonance (1H NMR) and infrared radiation (IR). The deterrent propellants are prepared by two kinds of typical gun propellants with polymer deterrent NA through water pattern. The diffusion of NA in the propellants are investigated by the means of accelerated aging tests, closed-bomb tests and interior ballistic tests. The concentration profiles of deterrent NA in the propellants before and after long-term storage are also studied by Fourier transform infrared microspectroscopy (FTIR Microspectroscopy). Test data indicate that there aren’t obviously change between before and after long-term storage in the explosion heat, p-t curves, interior ballistic and the concentration profiles. The results show that the anti-diffusing ability of NA is better and NA is suitable for the long-term storage of two kinds of gun propellants. The propellant fabricated with polyester NA is of well stability in the interior ballistic.
Interior Ballistic Modeling and Charge Structure Optimization of Cased Telescoped Ammunition
In order to improve the muzzle velocity of the cased telescoped ammunition (CTA) with a certain caliber, a kind of charge structure with the shear form when engraving the grooves of the CTA was designed, a theoretical interior ballistic model was established and the optimization design plan was proposed. Results show that the interior ballistic model can generally describe the interior ballistic characteristics of the CTA, the calculated results agree well with the experimental ones. On the basis, by optimizing the charge structure parameters of the CTA using the multi-objective particle swarm optimization algorithm, the muzzle velocity of the projectile is improved by 2.58% with the maximum chamber pressure unchanged. The study can provide reference for the interior ballistic modeling and the charge structure of the CTA.
Analysis of the Effect of RDX Particle Size in Propellant on Gun Interior Ballistic Performance
In order to improve the energy of the propellant ,a certain proportion of RDX was added into the propellant formulation. Through the text and analysis of the combustion performance of the propellant sample with 50μm and 10μm particle size RDX added by 100ml closed combustion apparatus, It is concluded that different particle size of RDX has no influence on the energy of propellant. Compared with the propellant containing 10μm particle size RDX,the propellant containing 50μm particle size RDX has higher burning rate index, abnormal burning rate under high and low temperature conditions,and higher burning rate temperature coefficient. The impact crushing test device was used to test the mechanical properties of the propellant with different particle size RDX at low temperature. It was found that compared with 10μm particle size RDX,the propellant with 50μm particle size RDX had more serious breakage and worse mechanical properties. By using zerodimensional interior ballistic model to carry out interior ballistic simulation calcelation and using artilley to carry out shooting test,It was analyzed and verfied that the propellant containing 10μm particle size RDX in the charge had better internal ballistic performance in the initial stage. The conclusion is that the propellant with different particle size RDX should be used in charge structure for different internal ballistic pressure range. This is provides a reference for the study of high-energy propellant and the study of the internal ballistic of barrel weapons.
Study on Impact Compressive and Tensile Mechanical Properties of HTPB Composite Base Bleed Grain at Various Temperatures
In order to investigate compressive and tensile mechanical properties of HTPB CBBG, split Hopkinson bar experiments were conducted. The strain rate varied from 1100 to 8000 s-1 at temperatures of 323 to 233 K. Non-linear true stress-true strain curves show that yielding is more significant at high strain rates or low temperatures. All true stress-true strain curves under compression have characteristics of strain hardening after yield point. The obvious stress drop after yield point of true stress-true strain curves under tension at high strain rates and low temperatures indicates that serious damage occurs and evolves. Based on the sensitivity analysis of yield stress to temperature and strain rate, it is found that the former has a more significant influence on compressive mechanical behaviors while temperature and strain rate have an evenly effect on tensile mechanical behaviors. According to the time-temperature superposition principle, the master curve of compressive initial modulus was built at reference temperature of 301 K and it matches well with experimental data.
Study on Optimum Design of Internal Ballistic Parameters of Fully Immersed Gun
The launching process of artillery fully immersed in the water is more complicated than that of in the atmospheric environment. In this paper, aiming at the launching process of fully immersed artillery, based on the classical interior ballistic model, the optimum design of internal ballistic parameters was conducted by using multiisland genetic algorithm. Factors such as the work of the projectile on the water column in the barrel, the water resistance of the muzzle and the influence of water depth are all considered. The loading parameters and propellant parameters, such as the chamber volume, projectile travel length, propellant web size, insensitive depth, surface burning rate coefficient correction, mass of charge, etc., are obtained which are satisfying the requirements of maximum bore pressure and muzzle velocity. Engineering analysis of the optimization results are carried out. This paper has certain reference significance for the interior ballistic design of underwater artillery.
Analysis of Overpressure in Bore Caused by Fragmentation of High Energy Gun Propellants
At the initial stage of launch, the propellants may break up in advance under the impact of the gas in the chamber, resulting in a sharp increase in the burning surface, which is an important reason for the formation of overpressure in the chamber and the initiation of the chamber explosion. In order to study this problem, the fracture model of high-energy propellants in bore under different shape parameters, material properties and initial temperatures was established. Then several kinds of propellant samples were tested by means of dynamic impact crushing equipment of propellants. And the experimental results were used to compare and correct the theoretical model. The modified model was coupled with the internal ballistic model to obtain the influence law of different degree of fragmentation of propellants on chamber pressure. Based on the above studies, the coupling model can simulate the overpressure in bore caused by the fragmentation of propellants and be used to analyze the conditions for the occurrence of overpressure. The results provide a basis for the design of new charging structure and the bore safety evaluation of ammunition.
Study on Mechanical Properties of ZTH Propellant
In order to study the mechanical properties of ZTH propellant, the impact test was carried out under the condition of normal temperature and low temperature, and compared with the AGu propellant. The particle breakage degree of the propellant is obtained by two methods of the weight distribution of the particles after impact and the initial stage of Γ-Ψ integral. It can be seen from the experiment that the breaking degree of ZTH propellant is larger than that of AGu propellant at normal temperature, but the degree of breakage is less than that of AGu propellant at low temperature. Through the comparison of two propellant mechanical properties test, it can provide a reference for the research of application of gun ballistic charge and the launch safety of the ZTH propellant.
Role of the Backward-Facing Steps at Two Struts on Mixing and Combustion Characteristiucs in a Typical Strut-Based Scramjet
The design of the strut fuel injector plays an important role in the performance of the strut-based scramjet combustor. The current study numerically investigates the flow and combustion characteristics of a scramjet combustor. An in-house code was developed to compute the Reynolds-averaged Navier-Stokes (RANS) equations coupled with the SST k ï€­ï· turbulence model and the one-step reaction finite-rate/eddy-dissipation model. In order to enhance the mixing and combustion efficiency, we develop a novel double-strut concept in the scramjet combustor. Firstly, the numerical methods are validated by the available experimental data in open literature. Then we compare the mixing and combustion performance between the single-strut and the double-strut cases. The numerical results show an acceptable agreement with the experimental results. The presence of the double struts has a remarkable enhancement on the mixing and combustion efficiency in the scramjet combustor when compared with the original single strut.
Discussion on Integrated Design Method of Internal Ballistic and Charge Structure of Multi-Ammunition
In this paper, the correlation between the internal ballistic and charging structure of multiple ammunition types and the tank system, turret system and fire system was established. The influence of gun interior ballistic parameters on gun chamber structure and barrel structure is analyzed. The influence of charging structure on gun bore structure, turret structure and tank structure was studied. The significance of this design method to the overall technical research of tank weapon system is summarized.
Burn Rate Evaluation with a New Design of Ballistic Evaluation Motor
In this work burn rate evaluation was carried out with a new design of sub-scale motor having 3kg propellant mass. The 3kg BEM when compared to the 40 kg sub-scale motor, commonly used in India, has several advantages. It poses less processing hazard and is also more suitable for conducting costly experimental formulations. The port configuration of the 3kg BEM was kept same as its 40 kg predecessor. The Klemmung, at all corresponding web thicknesses, could therefore be kept same. The L/D ratio of the 3kg BEM was reduced to 3 from a L/D ratio of 5 for the 40kg BEM. A new igniter was designed for the 3kg BEM and a reduction in ignition delay from 40ms to 24.5 ms could be achieved. The burn-rate obtained from the 3kg BEM varies w.r.t. the 40 kg BEM in the range (-)1.28% to (+)1.99%.
Analysis of Effects of Various Burn Rate Evalution Techniques and Process Variability on Bem Burn Rate Measurement
The burn rate for composite propellant is an important parameter which is required to be measured accurately for mission success. Burn rates for composite propellant are evaluated from the static test of BEMs (Ballistic Evaluation Motors) using pressure-time trace. Process Variability in BEM manufacturing such as bore offset, thermal shrinkage etc. results in a change in blowdown characteristics during burning of BEMs resulting in high burn rate bias in traditional burn rate evaluation method. Advanced analytical techniques for burn rate evaluation such as Hessler Glick, R ¸ Brimhall, Brooks etc. are used to mitigate these effects of process variability and arrive at reliable burn rates. The effects of traditional and advanced methods of burn rate evaluation on BEMs having different blowdown characteristics are studied. The advanced methods of burn rate evaluation are also compared to the traditional method and how the burn rate varies in these methods on BEMs having different blowdown characteristics.
Effect of Random Factors of Charge on Interior Ballistic Performance
In this paper, based on the sampling analysis of initial parameters of charge, such as propellant mass, arc thickness and combustible case mass, the influence of random factors on interior ballistic performance of charge is predicted by simulation calculation of random interior ballistic model. Firstly, the mathematical statistics analysis of initial parameters of charge is carried out to determine its distribution law. Secondly, the classical random interior ballistic probability model is constructed. The software is used to generate the initial parameters of large samples randomly, and a group of datum (7 rounds) is generated randomly from large samples. Through the model, carry out simulation calculation and analyze the influence of random factors on interior ballistic performance of charge.
Comparison of Methods for Prediction of Solid Rocket Motor Burn Rate
A solid rocket motor is the main workhorse for the strategic and tactical missiles. Burn rate is the most significant ballistic parameter for the performance prediction of solid rocket motors. In positive pressure exponent propellants, error in burn rate causes an error of greater magnitude in predicted ballistic performance. There are various methods for determiningpropellant burn rate such as strand burner, ballistic evaluation motor, etc. Ballistic evaluation motor (BEM) and strand burn data both are vital for composition finalization of the full-scale rocket motor. A correlation between BEM and strand burn rate provides a pathway towards performance prediction of the solid rocket motor. In this paper,burn rate of both methods for low and high burn rate compositions are analyzed and an attempt is made to establish a correlation for prediction of burn rate of a full-scale rocket motor.
Test and Analysis on Fault of Thyristor in a Pulsed Power Supply for EML
During the development of the pulsed forming units with rated storage energy of 100 kJ, a large number of thyristors used as the pulse switches were damaged. Based on the structure and equivalent circuit of the amplifying gate, the causes of the failure were found out by data comparison and analysis, fault component anatomy, process data investigation, gate resistance detection, turn-on time test and so on. The damage of thyristors was caused by the insufficient intensity of trigger current, which was rooted in the low operating voltage of the gate driving circuit. According to the conclusion of the turn-on time test, a method for determining design parameters of the strong trigger current has been obtained. The gate driving circuit was redesigned under the guide of the method. The new gate driving circuit has good performance, which entirely eliminates the hidden trouble of the failure.
Multiform Damages on the Rail of an Electromagnetic Rail Launcher
Electromagnetic launching technology is a new concept launching technology, which attracts much attention recently. Electromagnetic rail launcher is one of the many modes of electromagnetic launching technology. During the launch of the electromagnetic rail launcher, multiform damages have been observed on the rail in several electromagnetic rail launcher such as groove, gouge and erosion. An easily detachable electromagnetic launcher was designed to research the damages on the rail and some improvements were designed to reduce the damages on rails, such as high hardness and high conductivity material and coating technology. Results show that it can control the damages on the rails through selecting the appropriate rail materials and coating parameters. And these technical measures can also enhance the launch efficiency.
Numerical Simulation of Interior Ballistic Performance of Modular Charge by Two Models
In order to get the interior ballistic performance of modular charge, two models are established in this paper. A computer program is designed to solve partial differential equations in model A, an interior ballistic model based on the two-phase flow theory. In this process, the start-up pressure of projectile is measured by a large caliber artillery firing experiment. For model B, the finite element model of barrel and projectile is established by software Hypermesh and the motion resistance value is obtained using simulation software Abaqus with the fluid-solid coupling method. Comparing the simulation results with experimental data, although model B takes more time to complete the computational work, but with more accurate moving boundary conditions being used, it can improve the computational accuracy obviously.
Design and Manufacture of a 100kA Coaxial Pulsed Power Cable for Plasma Generator and PPS in ETC Guns
Based on our previous pulsed current and internal overvoltage test data and the experience of common commercial high power cables, a 100kA coaxial pulsed power cable is designed and manufactured to adapt the coaxial electric energy breech transmission between the plasma generator and the pulsed power supply (PPS) in electrothermal-chemical (ETC) guns. The index parameters are analyzed and determined. Semi-conductor layers and a shield stiffener are introduced to prevent the deformation and burst of the pulsed power cable structurally. The semi-conductor layer can eliminate the air gap and balance the electric field in the cable. The shield stiffener can multiply the mechanical strength to restrain the strong electrodynamic force produced by the core dislocation of the outer conductor. The multi-coupling of electromagnetic field, stress field and thermal field analysis are established to assist in aided design of electrical strength, mechanical strength and temperature rise characteristics. Both a DC voltage withstand test and pulsed discharge tests are introduced to verify and inspect the performance and dynamic response of the pulse power cable. The 25kV/5min DC voltage withstand test result shows that the sample leakage current is nearly 3μA and no abnormal phenomena of the pulsed power cable sample occurred. The pulsed discharge tests show that the sample can sustain the 100kA peak current. Furthermore, this 100kA coaxial pulsed power cable can satisfy the ETC test requirements. This paper is an extended abstract of a full paper that was published in Defence Technology, 2019.
The Utility of Piezoelectric Pressure Waveform in Muzzle Velocity Calculations
The article presents the fundamentals of piezoelectric pressure measuring technology in a barrel of a cannon during ammunition firing tests and focus on calculating the muzzle velocity using numerical analysis of piezoelectric pressure waveforms. Pressure measurement method by using piezoelectric transducer is very sensitive to outsource noise. Therefore, ballistic pressure readings are not always reliable especially when the diaphragm of the piezoelectric sensor is covered by burnt propellant remnants. Verification of correct value of pressure reading from piezoelectric system can be performed by comparing muzzle velocities. The paper presents reliability of pressure waveform in muzzle velocity calculations. The experiment took a place in MIAT in Poland during a routine ammunition tests.
Experiment of Combustion Completeness and Mechanical Intensity of Combustible Seals in Gun Propellant Charge
In order to reduce the combustion leaving of certain fixed cartridge gun propellant, the combustion completeness and the mechanical strength of combustible seals were studied. The compression tests of combustible seals and the conventional papery seals were carried out. The mechanical intensity of gun propellant charge with combustible seals was tested by ammunition ramming in gun weapon system and transportation on field road. The burning rates of combustible seals were tested by closed-vessel test. And the mechanical intensity and the combustion completeness of gun propellant charge with combustible seals were validated by interior ballistic test. The results show that the compression stresses of combustible underprop is two times as conventional paper underprop. The compression stress of combustible cover is about 40% as conventional paper cover. And it is about 80% as conventional paper underprop. The combustible seals can meet the demand of mechanical intensity for gun propellant charge in ramming and transportation. Under 50MPa ~150MPa, the burning rate of combustible seals is faster than 8 times as ADiGu gun propellant. The combustible seals can be burnt before gun propellant under the same burning environment in bore. And there is no combustion leaving in front of muzzle after firing.
Electrodynamic Response Study on Railgun Launcher Based on Electromechanical Coupling Model
The electrodynamic behavior of a medium caliber railgun launcher has been studied based on an electromechanical coupling model, which uses a unified modeling method for both electromagnetic and electromechanical field. This model adopts a material equivalent method to simulating the sliding contact behavior during armature in bore. An embedded node encoding program during meshing operation provides good load transfer accuracy between electromagnetic field and mechanical field. Dynamic properties of magnetic field are firstly simulated and a subsequent dynamic analysis is conducted by mapping element results from electromagnetic analysis step to structure analysis step. The electromechanical-elastic response of the barrel is studied under the current. The numerical model has shown reliability compared to experimental results.
Comparison of Computer Codes for Projectile Trajectory Simulation
BALCO is a newly introduced 6 and 7 degrees-of-freedom trajectory simulation software developed to compute high-fidelity trajectories of guided and unguided, fin and spin-stabilized, projectiles. However, its introducing paper draws some concerns about its fidelity; the presented results do not match those of the highly used and validated PRODAS trajectory module. The present work aims at discriminating which one of the two computer codes is erroneous and at suggesting, if required, potential corrections. Based on the performed analyses, which take a look at the erroneous test cases presented in BALCO introducing paper, both codes are valid; the observed differences are due to mismatches in the simulator inputs and Magnus moment models. However, the version 1.0b of BALCO is problematic anyway. When the projectile is fired with a sideslip angle, its initialization is erroneous. Also, for the simulation of finstabilized projectiles, its simplified aerodynamic model creates significant differences from PRODAS. The version 3.5.3 of PRODAS is neither free of concerns. As its attitude integration is done using Euler angles, it is sensitive to vertical dive discontinuity, which can be reached for some mortar nominal firing conditions.
Some Problems with Numerical Calculations of the Meteo- Ballistic Sensitivity Functions and Their Solutions
Projectile trajectories calculated under non-standard conditions are considered to be perturbed. Tools utilized for the analysis of perturbed trajectories are sensitivity functions: effect functions, weighting factor functions (WFFs) and appropriate Green’s functions. These functions are used for calculation of meteo ballistic elements ï­B (ballistic wind vector wB, virtual temperature τB, density ï²B) as well. Since 2013 we are working on improving the theory of these functions. We published the improved theory of generalized meteo-ballistic WFFs in the journal Defence technology in the year 2016 and then the improved theory of projectile trajectory reference heights in the year 2017. Using these theories will improve methods for designing firing tables, fire control systems algorithms, and meteo message generation algorithms. This contribution complements the previous two articles and is dedicated to the key problems of numerical calculations of the sensitivity functions.
A Comparison of Piecewise Cubic Hermite Interpolating Polynomials, Cubic Splines and Piecewise Linear Functions for the Approximation of Projectile Aerodynamics
Modelling and simulation of projectile flight is at the core of ballistic computer software and is essential to the study of performance of rifles and projectiles in various engagement conditions. An effective and representative numerical model of projectile flight requires a relatively good approximation of the aerodynamics. The aerodynamic coefficients of the projectile model should be described as a series of piecewise polynomial functions of the Mach number that ideally meet the following conditions: they are continuous, differentiable at least once, and have a relatively low degree. The paper provides the steps needed to generate such piecewise polynomial functions using readily available tools, and then compares Piecewise Cubic Hermite Interpolating Polynomial (PCHIP), cubic splines, and piecewise linear functions, and their variant, as potential curve fitting methods to approximate the aerodynamics of a generic small arms projectile. A key contribution of the paper is the application of PCHIP to the approximation of projectile aerodynamics, and its evaluation against a set of criteria. Finally, the paper provides a baseline assessment of the impact of the polynomial functions on flight trajectory predictions obtained with 6-degree-offreedom simulations of a generic projectile. This is an extended abstract of a paper published in Defence Technology, 2019.
Effect of the Firing Position on Aiming Error and Probability of HIT
This is an extended abstract of a paper to be published in Defence Technology, 2019. Sources of dispersions that contribute to delivery error and reduce the soldier performance in terms of hit probability are numerous. In order to improve the warfighter performance, the source of the errors contributing to the inaccuracy and dispersion of the weapon systems must be understood. They include ammunition dispersion error, gun dispersion, aerodynamic jump and the aiming error. The aiming error or gun pointing error is defined as the angle between the gun muzzle at the instant the trigger is pulled and the line of fire that corresponds to the intendent aim point. This is a round-to-round error. In weapons systems that include the rifle, the ammunition, a sight and a gunner, the aiming error was shown to be the single most important source of dispersion for the regular infantryman. In other words, for the general purpose rifle weapon system, the weak link is often the human. In order to verify and quantify this assertion, an experimental investigation was carried out to determine the aiming error associated with general purpose rifle fired by infantryman. The aiming error was evaluated for various firing positions and scenarios using infantryman for ranges varying between 100 m and 500 m. The results show that the aiming error is the main contributor to dispersion for the general purpose rifle fired by a non-specialized infantryman. The aiming error induced dispersion for unstressed and rested gunners is shown to be at best equivalent to that of the weapon fired from a bench rest by a marksman.
Analysis of Online Ballistic Parameters Filtering and Identification Method
To improve the range dispersion of range extended projectiles, a concise, effective, and low-cost technique, called One-Dimensional Trajectory Correction (ODTC), has been proposed and investigated. One of the critical issues pertinent to the development and application of ODTC refers to the online ballistic parameters filtering and identification. First of all, during the flight of projectiles, the effect of all kinds of random errors on the trajectory should be estimated online according to the flight data of range extended projectile in a segment of the trajectory measured by Radar or Global Positioning System. Secondly, the estimated effect is supposed to be quantified and represented by some characteristic parameters of projectiles. By using these parameters, the final range of projectiles can be predicted quickly and accurately, providing a reasonable basis for implementing longitudinal course correction. In this article, the online ballistic parameters filtering and identification method is to be discussed. In the process, some remarkable problems and its influence in practical engineering are also analyzed. The results are expected to be useful for further research.
Global Optimization of Aerodynamic Coefficient Identification Through Combined Multiple Measured Data of Projectiles
To improve the accuracy and validity of the aerodynamic coefficients extracted from free flight data for projectiles, this article presents a global optimization strategy of aerodynamic coefficient identification using multiple measured data of projectiles simultaneously. This strategy consists of two steps. In the first step, the local optimization algorithm is used in the process of independent identification for each projectile’s data individually to obtain the potential search space and then, in the second step, the Differential Evolution algorithm is used in the combined identification with the consideration of constraints. Finally, the proposed method is applied to a problem of aerodynamic moment coefficients identification using the angle of attack measured in a yaw card experiment. It is demonstrated that compared with traditional aerodynamic coefficient identification, the proposed one results in the global optimal solution and is of good stability and convergence. All the work is useful for further research.
Aerodynamic and Trajectory Characteristics of a Typical Mortar Projectile with a Deflectable Nose
Deflectable nose control is a new trajectory correction method. In this paper, the aerodynamic and trajectory characteristics of a typical mortar projectile with a deflectable nose are investigated with respect to its flight conditions. Using the method of wind tunnel testing, the aerodynamic coefficients of four kinds of mortar models were measured under the conditions of different angles of attack from -10° to 10° and Mach numbers from 0.3 to 0.9. Based on the aerodynamic coefficients, the trajectory ranges at different nose deflection angles and times were calculated. Furthermore, a trajectory optimization was performed by reducing the static margin. The results and discussions show that the nose deflection provided limited lift, while the pitching moment varied significantly. The mortar obtained the extended flight range and trajectory correction ability with nose deflection. This is an extended abstract of a paper that will be published in Defence Technology, 2019.
Aerodynamic Analysis of Optimized Bending Body Configurations with Trajectory Simulations
A bending body design of the Air Force Finner projectile was investigated as a maneuver technology with two different simulation methodologies, KESTREL and Cart3D, as well as an optimization algorithm. A strictly bent nose configuration was selected for focused investigation, the results of which informed the setup and execution of the optimization studies. The optimization studies identified similar optimal configurations—all strictly bent body configurations—for each Mach number investigated (2.0, 2.5 and 3.0). The strictly bent nose configuration was simulated in coupled Navier-Stokes trajectory simulations, which found up to 60 g of maneuver authority. Strictly bent nose and strictly bent body configurations as well as hybrid options were found to have similar performance with niche advantages in different ways that could be selected as control technology for extreme maneuvers.
Guidance of Medium Caliber Projectiles by Using an Impulse Thruster Coupled with a Navigation Module Based on Magnetometers-in-Flight Demonstration
The in-flight deflection of a 40-mm spin-stabilized projectile using a pyrotechnical thruster and a navigation module has been successfully demonstrated by the French- German Research Institute of Saint-Louis. Each of the technologies was previously validated separately by performing free-flight test campaigns at the ISL proving ground. In 2018, the two technologies were finally merged. Projectiles with an embedded thruster and a control electronics were fired at ISL at a Mach number of 2.2 over a distance of 230 meters. The very fast impulse is delivered by a reliable and robust pyrotechnic thruster containing only secondary explosive for higher safety and located at the projectile center of mass. The navigation electronics composed of magnetometers and a computing unit allows the real-time estimation of the roll angle, taking into account magnetic distortion effects. For the free-flight test campaign a total of 8 projectiles equipped with an impulse thruster have been manufactured, two inactive models (i.e. without pyrotechnical loading) to be used as references and six active models to test the reproducibility of the deflection direction and amplitude. It was demonstrated that these latter are deviated in the expected direction from their nominal flight path by 80 cm at a remaining distance of 150 meters from the final target. The expected deviation direction is obtained thanks to the perfect synchronization of the thruster having a jitter of only ±6 μs with the 670-Hz roll angle estimation. Successful results were confirmed by video recordings and impact points determination on the net target.
A Study on the Effectiveness of a Multiple Rocket Launcher (MRL) with Unguided Rockets
Multiple Rocket Launchers (MRL) have been used for an army weapon system over the past several decades. In this study, we have predicted effectiveness for MRL with a certain unguided rocket. ARTQUIK model has been used to calculate requirements of rocket with Target Location Error (TLE), lethality of warhead and target size. Needs for rocket sharply increased by about 170% with TLE. Enhancement of lethality helped to reduce amount of rocket. Especially, it rose by five times with TLE in the tiny target size of below 50m. However, a number of rocket increased by three times with TLE in the large target size of above 150m.
Visualization of Muzzle Flow and Projectile in Flight Flow Using the Background Oriented Schlieren Technique
The present paper focuses on the development of a non-intrusive measurement technique and the implementation of a quantitative flow visualization method based on Background Oriented Schlieren (BOS). The gun muzzle flow, the aerodynamics, and the ambient airprojectile interaction are visualized. In BOS, the experimental set-up of conventional Schlieren (mirrors, lenses, and knife-edge) is replaced by a background pattern and a single digital camera. The proposed measurement technique and the implemented algorithm are first validated through the temperature measurement of a flame-induced distorted flow field. An acceptable accuracy is recorded, the measurement error being less than 3-5% of the full scale. Second, the muzzle flow and the flow field around a 5.56 mm projectile in free flight was captured and analyzed. The captured structures such as vortex, barrel shock, Mach disk, and blast wave show a good agreement with those issued from the conventional Schlieren set-up
Coupled Simulations for a Canard-Controlled Projectile with Thrust-Vector Control
This paper describes a computational study to understand the aerodynamic and flight dynamic behavior of a canard-controlled, fin-stabilized body with thrust-vector control (TVC) at a supersonic velocity. Numerical simulations have been performed for this projectile with TVC using an advanced coupled computational fluid dynamics (CFD)/rigid body dynamics (RBD) technique. The coupled CFD/RBD method allows time-accurate, virtual fly-out simulations of projectiles and simultaneously predicts the aerodynamics and the flight dynamics in an integrated manner. The jet control maneuver is achieved by the nozzle located in the rear section of the projectile. Computed results show the actual time-dependent response of the flight vehicle and the resulting unsteady aerodynamics and flight dynamics with jet control for a variety of conditions. Comparison of total angle of attack results with and without the thrust nozzle deflected indicates that the coupled calculation automatically captures the relevant jet interaction physics resulting in high angle of attack flights.
Influence of Crossing the Transonic Domain for Precision Ammunition
Although trajectography for small-calibre and long-range projectiles in particular, seem to be controlled since a long time, it is not totally mastered within transonic or even subsonic range. Given the high cost of the precision ammunition and the increasingly complex practical execution of the firing process due to the required distances, the use of Computational Fluid Dynamics is clearly an added value. However, since numerical simulations have very little value without a solid experimental basis, this study aim to establish the pillars for numerical modelling of these projectiles in the transonic domain. By means of studies carried out in the past and relatively new flow visualization techniques (Schlieren + Background Oriented Schlieren), the precise quantification of the drag as well as the various shocks propagating in the transonic domain were determined, with good agreement between all techniques.
Adaption of Modified Point Mass Model for Efficient Trajectory Parameters Computation of Artillery Rockets
The modified point mass (MPM) model is principally used to simulate trajectories of spinning projectiles. In this paper modified point mass model is used to simulate the trajectory of unguided rocket. The result of the modified point mass model tuned for drag and tipoff are compared with six degree of freedom trajectory (6 DOF) model. The difference between tuned MPM and 6 DOF calculation for maximum velocity, maximum spin, range, vertex height, time of flight, angle of descent and impact velocity is less than 0.13% for all the elevations. The MPM also gives reliable and acceptable result for all standard and nonstandard conditions with compare to 6 DOF. MPM can be a good choice even for artillery rocket trajectories where computation time is critical parameter to select the model.
Simulation of Continuous Shoot Precision for Remote Controlled Weapon Station
Shooting accuracy is one of the important indicators of remote controlled weapon station. Based on the dynamics analysis software adams, a virtual prototype of a remote weapon station was established estimate the influence of control system error on system accuracy. simulation and analysis of dynamic characteristics of shooting. Verify the structure and principle of the system. inspection of fire control performance and obtain the shooting accuracy of the weapon system. Comparing with the firing accuracy of live ammunition. The correctness of theoretical and simulation analysis is verified. The research and improvement of firing accuracy of the weapon system has certain guiding significance, and has certain reference value for the design and research of modern digital weapon system.
Latest Trends in Ignition Systems and Related Aerospace Mechanisms Technologies to Empower Interior and Exterior “Ballistic Transientsâ€
In order to Empower “Ballistic Transientsâ€, Ignition Systems and Related Aerospace Mechanisms are the key technological areas to perform their mission critical functions under harsh environments. This is a fascinating subject covering the full ambit of Engineering offering unlimited scope for innovation, design, and manufacturing skills. However many new technological advances have swept into face new challenges in this mission critical areas. Presently many space missions, Defence missions, Rendezvous interplanetary crafts, Stationary space platforms, landing modules, Earth probes. Optical astronomy and Soft docking systems are utilizing newer technologies. These activities are presently utilizing laser initiation, pyrogen jets, digital initiation, thermoelectric initiation, Energetic materials, Smart mechanisms, Shaped memory alloy mechanisms, Mems actuators and Non Explosive Actuators to deal with this key technological areas. Looking forward for a giant leap towards smart, stronger, robust, reliable systems to empower ballistic applications, this paper covers all these new areas of interest, bringing an insight exposure in to the advances and futuristic challenges.
An Innovative Stabilizer Unit Design for Tube Launched Artillery Rocket to Improve Dynamic Stability
In this paper, stabilizer unit of the tube launched artillery rocket is designed with flat wrap around fins (WAF). A comparative study has been carried out to find out the aerodynamic behavior of same rocket with curved and flat WAF. Computational fluid dynamic (CFD) is used to find out aerodynamic coefficients of the rocket with both types of fins. It is found that with flat WAF chances of occurrence of out-of-plane moment reduced drastically. Hence, it is recommended to use Flat WAF for tube launch rocket to avoid any
Simulation Analysis on the Aerodynamic Characteristics of Jacketed Rod During Hypervelocity Flight
The jacked rod is new kind of kinetic projectile with high length-to-diameter ratio that deal with the armor target in the battlefield. The Jacketed rod consists of a central high-density core surrounded by a low density jacket. Compared with ordinary long-rod penetrator, the aerodynamic characteristics of the jacketed rod are different because of the jacket structure. In this paper, the external flow field of the jacketed rod is simulated using the computational fluid dynamics software FLUENT. The aerodynamic shape of the jacket is changed to observe the flow field around the rod and obtain the corresponding aerodynamic parameters. The main consideration of the aerodynamic shape includes the shape of the front and rear ends, the recessed or convex groove of the ring groove and the disturbed flow between the annular teeth. By analyzing the variation of aerodynamic parameters, the influence law of jacket shape on aerodynamic characteristics are obtained. 1. The cone angle at the front end of the jacket greatly reduces the air resistance of the jacketed rod. 2. Though boat-tail angle has the optimal value to minimize air resistance, the effect of it on air resistance is negligible when the jacketed rod is during hypervelocity flight. 3. The jacket with the convex teeth causes an air resistance of 30 to 35% larger than that of the jacket with concave teeth. 4. The resistance caused by the disturbed flow between the annular teeth of the jacket accounts for approximately 25~27% of the total air resistance. Finally, the optimization opinion of the structure of the jacketed rod is proposed from the aerodynamic layout.
Aerodynamic Coefficient Reconstruction of a Controlled Spin Stabilized Projectile Using Mono and Multi Fidelity Surrogate Models
The trajectory of a 155 spin-stabilized controlled projectile is reproduced using surrogate models. RANS evaluations of a spoiler aerodynamic coefficients constitute a kriging database. The mono-fidelity surrogate model is unable to reproduce the evolution of the aerodynamic coefficients. A second level of fidelity is constituted of wind tunnel measurements in the definition of a cokriging model. The measurement points are chosen using an exchange algorithm over the available data. The inclusion of three experimental data points in the cokriging database improves greatly the accuracy of the coefficients estimations, leading to the quasi reproduction of the trajectory.
In-Flight Spin Measurement of High Velocity Projectile Using Infra-Red Imaging Technique
In the present study, a novel methodology for the measurement of spin of canon launched high calibre supersonic projectile using the techniques of high speed Infra-Red(IR) imaging has been presented. It has greatly reduced the tactical disadvantages of conventional painting method of synchro-ballistic spin measurement. The nubs on the projectile surface get heated due to friction with the inner surface of gun barrel during in-bore motion. The heated nubs act as the marker for spin measurement. Spin value measured using this methodology is found to be in good agreement with theoretically estimated spin value.
Elevations for Maximum Ranges of Projectiles
Ballistic performance of Artillery projectiles are generally characterized by maximum range and dispersion. Launch angle at which maximum range is achieved by a projectile for a given combination of weapon and charge has been a long intriguing aspect for Ballisticians. Although in ideal conditions, vacuum, trajectory case maximum range of a projectile is achieved at an elevation of 450, below which the range decreases monotonically with decreasing elevation and beyond which the range reduces with increasing elevation. But in actual scenario, presence of air, which offers drag to projectile motion largely affects this value. A review of theoretical considerations and computational verification of the same with various projectiles have been carried out to establish the relationship between various factors that characterize and determine maximum ranges. This plays a vital role for computational purposes like Fire Prediction and Firing Tables compilation. Termination conditions of most of these Ballistic algorithms essentially built around these data. For the sake of brevity and want of completeness a few projectiles were only studied. Projectile classes considered have been varying in their sizes from 0.303cal Bullets to 305mm Artillery shells, masses from few grams to few 100s of Kgs, with L/D ratios from 3 to 25 and fineness varying from blunt noses to highly Ogival shells. Detailed trajectory computations based on Point mass trajectory model has been attempted to answer and to offer plausible explanations for the not so obvious problem.
Effect of Fin Cant Angle on Coning Stability of an Unguided Artillery Rocket
This paper presents the flight stability studies of an unguided artillery rocket with curved wrap-around fins. Due to asymmetry in the flow field around the fin, curved wrap-around fins unlike the planar fins exhibit special aerodynamic characteristics such as induced roll moment, roll reversal through supersonic Mach number, excessive side force and out-of-plane moment. The out-of-plane moment if not carefully controlled can lead to severe coning motion of the rocket causing flight instability and catastrophic failures. Such an artillery rocket which encountered failures in several flight tests due to poor dynamic stability is considered for the study. The aerodynamic characteristics of the rocket with different fin configurations is obtained from wind tunnel tests and analyzed to identify the parameters causing the instability. Coning motion stability analysis of the rocket is carried out for all its configurations to identify the existence and behavior of the instability. The results obtained from the analysis shows that the stability of the rocket improved, by reducing the out-of-plane moment. Hence, a suitable curved fin configuration is proposed with reduced fin cant angle, to reduce the out-of-plane moment and improve the dynamic stability of the rocket. Trajectory simulation of the rocket with both the fin designs is carried out to visualize the improvement in the performance of the rocket. Flight tests of the rocket with reduced fin cant angle was carried out and the configuration achieved the desired range with excellent flight stability and consistency.
The Release Region Design of Guided Bomb Attacking Ground Maneuvering Target by Pattern Search
Due to the characteristics of the ground maneuvering targets like the armored vehicles, the interference of the ground background noise and the poor maneuverability of the guided bombs, it is not easy to strike the maneuvering target on ground effectively using the guided bomb. To deal with the aforementioned problems, the relative movement of the target and the guided bomb is analyzed in 3-D reference frames, and the impact angle constraint is added in the terminal segment of the guided bomb’s trajectory. As a result, the guided bomb can achieve an effective killing on such targets with an overhead-attacking guidance law. Based on this overhead guidance law, the release region of the airborne-antitank guided bomb is designed in different situations using the pattern search algorithm. The design of the guided bomb’s release region has greatly reduced the difficulties for the operators to achieve the attacks, which is extremely meaningful in actual combat.
Parametric Aerodynamic Evaluation & Design of Curved Brake Ring
An artillery rocket generally utilises wrap around fin (WAF) assembly to provide static and dynamic inflight stability. Wrap around fin configuration poses additional advantage in terms of compact storage in launcher tube. However, rocket with wrap around configuration are susceptible to coning instability due to out of plane moment generated at certain Mach number and angle of attack combination due to curvature of the fin plan form. An artillery rocket is designed to perform certain intended operations. Rocket under consideration is designed to be used specifically in mountainous region and is intended to be fired at higher elevation to achieve minimum range of 12 km after crossing a cliff or two. The same rocket when fired with proximity fuze, poses additional requirement of specific angle of impact for desired target end effect. To meet explicit demand on angle of impact, fireman’s control on choice of angle of elevation is lost, which is a dictating factor to achieve minimum range by the rocket. This poses a need to design a mechanism by which the range reduces and the angle of impact for particular AoE increases, while maintaining rocket’s inflight stability. In presented work, drag augmentation mechanism is designed for a medium range artillery rocket which is fired with proximity fuze and uses WAF for providing in flight stability. WAF configuration combination with drag augmentation device is analysed crucially for side force generation point of view. Extensive CFD simulation is done for all rocket configurations and CFD data is validated using wind tunnel analysis for one of the design. An in house Six degree of freedom (DoF) trajectory model is utilised for flight performance prediction. Flight test is conducted for the finalised design and it matched well with the predicted data. A suitable design of brake ring maintaining required static & dynamics stability is finalised for rocket’s minimum range performance.
Six-Dimensional Ballistics of a Certain Howitzer Projectile Considered with Dynamic Unbalance
The fabrication error and assembly error of warhead and fuse will cause the dynamic unbalance of howitzer projectile, which will bring a negative impact on the safety and reliability of fuse. In order to obtain the motion of a certain 155 mm howitzer projectile on the exterior ballistics, the six-dimensional rigid body motion equations of the projectile were studied. The aerodynamic parameters which needed for the six-dimensional rigid body motion equations of the projectile’s exterior ballistics need to be obtained by simulation. Firstly, the credibility of the simulation method is verified in this paper. Then the aerodynamic parameters of the projectile are obtained by numerical simulation of the projectile flow field. When solving the six-dimensional rigid body motion equations of projectile exterior ballistics, the dynamic unbalance of projectile is considered. The calculation results are very important for the safety and reliability of fuze on the projectile under the condition of dynamic unbalance.
Assessment of Monocular Optic Flow Analysis for Ballistic Trajectories
This paper describes a preliminary study to assess the potential optical-flow performance of a simple on-board camera to provide a low cost navigation solution for unmanned systems such as drone aircraft or other types of projectiles. For decades, complex electronics systems such as the Global Positioning Systems (GPS) and sophisticated inertial measurement units equipped with rate-gyroscopes and accelerometers have proven to be very accurate for navigation updates. However, these systems are costly and may be prohibited from proper function under adverse conditions. For this study, 3D scene generation software developed by Diamond Visionics was used to simulate the view of a forward-looking camera system during a ballistic descent. The algorithm tested for this study does not perform geo-registration to match known locations on the ground from reference imagery, but instead relies only on knowledge of the intrinsic parameters of a properly calibrated camera/lens system for measuring orientation updates and has the potential to measure changes in absolute position provided that another source of velocity (such as a priori estimates or additional sensors) is available. Preliminary results show that reasonable estimates for projectile position and angular rates can be made. These results are made even more accurate when using a tuned bundle adjustment algorithm.
Achieving High Maneuverability and Precision in Munitions Using Non-Linear Flow Interactions
The work presented seeks to achieve high level maneuverability in highspeed weaponry using flow actuators that have very small footprint. The principle of generating such large control forces and moments is by leveraging the non-linear flow interactions that occurs with a distorted boundary layer and the control fin shock. Well-quantified distortions are generated via micro-ramp vortex generators (VG) to embed strong streamwise vortices into the boundary layer. These VGs are 1.0 and 0.6 incoming boundary layer thicknesses tall, and their geometries are configured for maximum distortion strength. The distortion magnitude determined based on the mean difference in the streamwise velocity from the undistorted boundary layer, integrated over boundary layer height, is between 20% - 34% for a M = 2.5 boundary layer. The control forces and moments are determined using the mean surface pressure field for different VGs placed at different azimuthal locations with respect to the fin leading edge. These configurations resulted in up to 15%, 18% and 24% change in the fin-normal force, rolling and pitching moments, respectively, compared to the unperturbed results. The impact on the pitching moments provides compelling evidence that perturbing the boundary layer and exploiting the associated fin-generated shock boundary layer interactions is a viable strategy to enable high maneuverability in munitions. This summary contains 208 words.
The Research on Falling Position Prediction Method of Long Range Guided Rocket Based on Surrogate Model
A novel strategy of predicting falling position based on surrogate model is proposed for meeting the urgent needs of quick and accurate prediction of falling position for long range guided rocket. Through applying surrogate model methodology, this method is established a highly nonlinear functional relationship between falling position, ballistic parameters and launch elements, which relationship is used to predict quickly and accurately for guided rocket’s falling position in any launch conditions. Under the comprehensive consideration of flight status parameters and launch elements that influence accuracy of prediction of falling position, PRS, Kriging and RBF are implemented respectively in the research of falling prediction during climbing section and falling section of the guided rocket. Finally, numerical simulation compares and analyzes the accuracy and rapidity of various surrogate models, the effectiveness and practicality of the method are demonstrated.
Experimental Studies on Velocity Attenuation Characteristics of Projectile Fragments
Using smooth-bore gun to launch projectile fragments with different muzzle velocity and shapes, the characteristics of the fragment velocities changed from the distances were achieved by velocity measurement system. The velocity attenuation coefficient and the air drag coefficient of fragment with different shapes were calculated based on the theoretical model and experiment results. The results show that the velocity-hold capacity of spherical fragment is better than cylindrical fragment and cuboidal fragment. The velocity attenuation coefficient and the air drag coefficient are related to the muzzle velocity. The variation of air drag coefficient has an opposite tendency to the muzzle velocity in the range of 1300 to 2100 meters per second.
Parametric Profiling of Water-Jet Projectiles for EOD Disruptor Using High-Speed Imaging Technique
Parametric evaluation of frangible projectiles, like water-jet for disrupter applications and explosively formed shape charge projectile is essential to assess the behavior and impact effect of the projectile at the target end. Being as frangible in nature parametric profiling of such projectiles are challenging as compared to solid projectiles. Available conventional methods for such type of measurement are limited to either average velocity of the projectile or only terminal effect at the target end. Parametric behavior analysis by conventional methods requires number of iterations and it’s not cost effective. This article presents the novel non-contact methodology for parametric profiling of water-jet projectile using highspeed imaging technique in the external ballistic zone. The proposed methodology can generate the continuous profile of velocity from muzzle exit, which is useful to analyze and assess the behavior and impact of a water-jet projectile in the zone of muzzle exit, inflight and the target point depending open field of view of imaging system.
A Novel Approach for Launch Opportunity Calculation for High Inclined Orbit Mission
This paper presents an elegant method to calculate the launch opportunities for injection of satellite into the highly inclined orbit by a launch vehicle from a specific launch site. The launch vehicle should inject the satellite in the desired orbit satisfying all orbital parameters. The launch window for a highly inclined orbit is highly critical since desired Right Ascension of Ascending Node (RAAN) and Equatorial Crossing time should be as close as the desired parameter, which if not achieved will result in the orbital maneuver requirement from the satellite. Most of the small satellites cannot afford to carry out an orbital manoeuver due to lack of adequate fuel on-board satellite. This becomes still critical in case of multiple satellite launch from a same launch vehicle. In order to directly meet the plane of the orbit from a given launch site the launch vehicle must be launched inside a narrow window. An approach to calculate launch azimuth for a desired orbital inclination and launch time for desired right ascension of ascending node with a given launch site is described in this paper. This paper also describes an efficient and generic method by considering orbital geometry to calculate an optimal launch window which can take care of orbital parameter requirements of multiple satellites from a single launch vehicle also.
Establishment of New Method for Evaluation of Ballistic Consistency
Regarding problems arisen from evaluation of ballistic consistency of two kinds of projectile with two different parents via two common evaluation methods of average ballistic consistency, the statistical function is presented herein to test average ballistic consistency of two projectiles according to basic concept of ballistic consistency and the difference in characteristic value of drop-point dispersion ellipse between two projectiles. Maximum allowable value of two dispersion ellipse centers and the test and evaluation criterion are derived from the concept of equivalent hit probability. Relevant sample size calculation equation and OC (Operating Characteristics) Curve are applied to determine relationship between the predetermined efficacy of test and minimal sample size of test, so as to provide an effective means for decision and planning of sample size before test, and determination of test efficacy after test. The effectiveness and practicability of the average ballistic consistency evaluation method established herein are verified by comparison test of 3 groups of 8 high explosive bombs (Burst Cartridge) and large power bombs for a howitzer, and shot by shot shooting comparison test of 1 group x 4 high explosive bombs and Smoke Projectiles.
Research on Application of Low-Cost Strapdown Inertial Navigation System in Initial Input Phase of Short-Range Surface-to-Air Missile
Aiming at the problem of radar interception and beam introduction in the initial stage of launch of a rotating surface-to-air missile, a low-cost strapdown inertial navigation device is proposed to replace the interception radar. This method makes full use of the characteristics of surface-to-air missile rotation, modulates the measurement signal of strapdown inertial navigation device by the rotation of missile body itself, realizes automatic compensation for errors such as drift, bias, cross-coupling of channels, installation deviation and so on, and improves navigation accuracy. The simulation results show that the rotation modulation of the missile body can significantly suppress the influence of the above errors on the navigation accuracy, and has the ability to replace the interception radar to complete the initial interception and beam introduction.
Analysis & Modeling of Delay in HILS of Aerospace Systems
Embedded systems can be developed and evaluated by using a testing technique which is used increasingly known as Hardware In Loop Simulation (HILS). HIL simulation provides an effective platform for real time embedded systems development and testing. The avionic sub systems like sensor and actuators are included in the HILS test bed for evaluation of their real time dynamic performance. The Flight Motion Simulator (FMS) is used to simulate the angular rates of vehicle body rotational motion. The physical systems along with numerical simulations and hardware interfaces in the HILS test bed create a considerable delay during simulation runs. This delay leads to unwanted oscillations in the HILS results. Under this scenario the HILS cannot be performed to evaluate the Avionic sub systems. This paper describes thorough analysis of the delay aspect in the HILS runs and modeling of delay in Real time (RT) simulation for understanding its effect. This summary contains 147 words.
An Analytical Approximation for the Distribution of the Extreme Spread of a Shot Group of N Rounds
The purpose of this paper is to propose an analytical approximation for the inverse cumulative distribution function (ICDF) of the bivariate range (commonly referred to in the ballistic community as the extreme spread (ES)) of the circular normal distribution. A proof is given to show that the relative error of this approximation is less than 1.37% for any sample size and any percentile. Monte Carlo simulations are run to verify the results of the analytical approximation. In addition, the exact ICDF for the case of three sample points is determined.
Applying the Method of Normal Forms to Nonlinear Angular Motion of Projectiles
The modern development of missiles and projectiles that have shown that nonlinearities, usually ignored in traditional ballistics, have a significant impact on the flight performance of projectiles. However, the complexity of the high order terms coupled in the angular equations and the lack of appropriate analytical tools have hampered the investigation of these effects. In this paper, the method of normal forms, featuring transformations that can simplify the dynamical system equations, is applied directly to the angular motion equation to obtain a simplified formulation for the nonlinear angular problem. Analytical solutions are obtained under quantic static moments. Numerical simulations are carried out to demonstrate the efficiency and accuracy of this method. Besides, a criteria identifying the stable region of initial angle of attack is derived and examined feasible and effective. The results of this research can contribute to the studies of more complicated problems related to nonlinear angular motion.
GPU Accelerated Trajectory Simulation for Large Scale Monte-Carlo and Optimization
For large systems of systems modeling and simulation studies it is often required to perform a multitude of simulations with parameter variation to evaluate the control system strategy or overall system performance. Evaluations of these parametric studies for small systems is often trivial and may be completed on a desktop computers, whereas larger systems, with run times greater than real-time, porting to a cluster is often necessary. With the improvement of General Purpose Graphics Processing Units (GPGPU) computing capabilities, it is more tractable to port models to GPU kernels for parallel execution. This paper demonstrates the use of graphics processing units for Monte Carlo trajectory analysis with the intent of optimizing flight trajectories and improving guidance laws. A variety of approaches are attempted to port a legacy simulation for a guided mortar application to a code base which may be run on a GPGPU with the objective to minimize the introduction of error and improve workflow for the systems engineer. Historically, this process is time intensive and requires deep understanding of the implementation details for the hardware. The approach is to minimize the human translation of code from one language to another (Ex: Simulink to NVidia CUDA) and utilize modern methods and libraries to perform this translation and optimization. The paper will describe the integration of high performance codes and compilers to demonstrate large scale simulation and speedup of trajectory simulations.
Optical Analysis of Probe Movement in a Ballistic Measuring Module
The use of optical imaging is limited at all stages of the ballistic cycle when accelerating probes in launchers. The developed technology of visualization of ballistic processes allows investigation in detail the process of acceleration of the probe in the guiding element of the launcher - in the barrel gun installation. The result of the study was the establishment of ballistic parameters of private versions of the launcher. The values of the ballistic parameters registered in the implemented launcher are used to check the tasks of mathematical modeling and to obtain additional information about the features of physics and the parameters of the process of internal ballistics -the history of changes in the working mixture, about the work of probes elements at stages of the ballistic cycle, about dynamics of the probe acceleration, about dynamics of the gas flow.
Soft Recovery of Gun Launched Supersonic Projectiles in Long Column of Compressed Air & Water
This paper discusses about development of testing methodology where fuze electronics is exposed to severe gun launch acceleration and softly recovered in decelerating setup so that survivability of fuze electronics can be tested against severe gun launch exclusively. An indoor facility based on ballistic compression concept has been developed. This consist of 40 mm smooth bore gun to launch the projectile and 33m long tube having slotted section, free air section, pressurised air section and incompressible water section separated by composite diaphragms. Parametric study was carried out in NASTRAN & AUTODYN using explicit analysis in Eulerian and Lagrangian domain to simulate supersonic projectile deceleration profile in compressed air column followed by water column. An ogive-nose cylindrical projectile was launched by gun in muzzle velocity range of 350 m/s to 800 m/s and successfully recovered in this designed soft recovery setup. Simulation results were found in correlation with experimental results.
Analysis of Muzzle End Behaviour of Tank Gun Barrel with Sand Ingress During Ammunition Firing
The current work presents a detailed study of 125mm tank gun smooth bore barrel behavior during sand ingress while firing with HEF (High Explosive Fragmentation) projectile. Large number of failures and defects at muzzle end region of 125 mm smooth bore tank gun barrels was observed, especially in field firing ranges. The obstruction due to sand deposits lead to high velocity impact between the sand and barrel, which causes large barrel bore radial deformation and results in material failure. To understand this effect of sand deposit, field trials are conducted. Further, a series of 3D numerical computer simulation and analysis using ANSYS - Autodyn software are done. The field trials and analysis clearly demonstrates that, presence of sand obstruction beyond threshold quantity leads to permanent deformation of barrel bore into elliptical shape or breakage of barrel.
Development of High Strength Extended Range Full Bore (ERFB) Projectile Body for Futuristic 155MM Artillery Guns
Quest for range enhancement has led to development of Artillery Guns which are capable of generating high pressure levels in the tube to propel the projectiles at increased muzzle velocity. This leads to increased level of launch forces the projectiles are subjected to. Survivability of the Extended Range Full Bore (ERFB) projectile body has been assessed for exploitation with different class of 155mm Artillery Guns. An approach for development of high strength ERFB projectile using existing geometry, raw material and manufacturing set up has been devised, wherein heat treatment process has been altered suitably. Large scale destructive testing of prototypes for evaluating the enhancement in mechanical properties has been carried out. The approach has been validated by conducting dynamic evaluation trials. Static trials for comparing the fragmentation effect of existing and high strength ERFB projectiles have been carried out and the latter have been found to exhibit better performance.
Research on Momentum Transfer in Simple Railgun
In this paper, the momentum conservation equation in the longitudinal direction for simple railgun was deduced. In this model, a space V with variable volume is taken as the research object. The electromagnetic surface force on the outer surface of V is equal to the sum of the mechanical momentum received by the guide rail and armature in space V and the momentum of the electromagnetic field in V. Then, a three-dimensional model was established and the finite element method was utilized to simulate the problem. Based on the simulation, some results such as the surface force on the electromagnetic field, the electromagnetic force on the conductor in the longitudinal direction were obtained. Compared with the external surface force FSx = 2938.6N and the electromagnetic force Fmx = 2938.7N on the conductor, the electromagnetic force of the electromagnetic field Fex = 6.37e-16N can be ignored. So the volume force Fmx could be characterized by the surface force FSx. Furthermore, results showed that of the six surfaces of V only the longitudinal section surface force FSx(S0) and FSx(Sx) contribute to FSx. It reviewed that the momentum of the railgun system was conserved when the surface force of the electromagnetic field was contained. Then, the surface force density on different longitudinal section of railgun was analyzed and discussed in details. It is showed that the surface force density gradually concentrated from the outside air to the area between the rails. In addition, the surface force disappeared instantly after passing the armature. It reviewed that large amount of longitudinal force was transmitted to the breech by the electromagnetic field in the form of surface force. And the specific position and distribution of recoil were related to the current input device in breech.
A Finite Element Model to Predict the Influence of Asymmetries on Barrel Dynamics in Small Arms
Appropriate boundary conditions, particularly asymmetries, are critical to modeling the dynamics of small arms barrels. Lateral barrel vibration, an important factor governing small arms accuracy, is primarily driven by the recoil couple created by the distance between the barrel-axis and the center of mass of the firearm. This paper presents a computational model which includes the action geometry in order to capture these physics. Solved using Abaqus/Explicit, this model features parameterization through Python scripting. Barrel parameters include length, contour, caliber, chambering, and rifling pattern. Action geometry and projectile are selectable from manually created model libraries. Model features include spatially and temporally varying pressure loading, gravity loading, projectile-bore interaction, projectile plasticity, and representative masses for geometry not explicitly included in the model. The long-term purpose of the model is to investigate the sensitivity of the muzzle exit condition to firing cycle initial conditions for barrels of variable geometry and composite construction.
A Numerical Analysis of the In-Bore Motion of Small Caliber Projectiles
Finite Element simulations have become a popular tool to investigate the mechanisms of launch dynamics. However, the common techniques for evaluating the simulation results in terms of target impact accuracy are far from ideal. This paper presents a method for the postprocessing of such simulations. The approach is based on a decomposition of the bullet’s transverse motion during launch into a regular rotation caused by the rifling, irregular oscillations (balloting) and muzzle motion. Target impact dispersion is evaluated separately for each of these motion components, which provides a deeper understanding of the dynamic processes determining the weapon’s hit performance. In contrast to traditional methods, where the assessment of dispersion requires large numbers of simulations with varying launch conditions, the evaluation of accuracy is based on a single simulation.
Launch Dynamics of a Canisterised Missile
Vibration of a missile canister during launch can damage the missile. Understanding this dynamics is a vital aspect of launcher design. A detailed system level finite element model was made including the launcher, missile and various systems. Transient dynamic simulation of the launch was performed subsequently. The model was validated by experimental measurements of launcher vibration. Using the model, an insight was obtained on dynamics of launcher missile interaction. The safe launch of the missile was ensured. The modeling approach was experimentally validated.
Flexibility Analysis of Cylindrical Panels of a Hypersonic Launch Vehicle in a Ballistic Trajectory for Separation Loads
Nose cone and cylindrical panels of a hypersonic launch vehicle encapsulates cruise vehicle during boost and coast phase of ballistic trajectory. At predetermined altitude and Mach number panels open, rotate about a hinge and separate from launch vehicle so that cruise vehicle can be ejected for autonomous flight. Objective of the study is to ensure that cylindrical panels are integral while rotating about the hinge and once released, move away from cruise vehicle. Design objective is achieved by performing a transient dynamic analysis of cylindrical panels with varying pressure loads using commercial finite element software ANSYS. In this analysis, a pair of cylindrical panels is modeled simultaneously. Hinged boundary condition is simulated up to release angle. Panel release condition is simulated by removing the boundary conditions at the appropriate time step. Stress distribution on panels and panel deformations are evaluated. Observations from study are, for high release angle, panels fail and disintegrate however at very low release angle it tends to interfere with the cruise vehicle. Design objective is met by a release angle of 10 deg. Rear end ring thickness is increased to reduce stress and large deformations. Factor of safety on panels are within allowable limits for a release angle of 10deg.
Theoretical and Experimental Analysis of Small Arms Jump for Classic and Bull-Pup Layout
The main task of presented hereby work was to verify thesis about better accuracy of bull-pup rifle comparing to classical layout. The jump angle was assumed as a crucial factor influencing accuracy. Such comparison was possible due to the fact, that both rifles used in tests belonged to the same weapon family – Modular Small Arm System. Physical and mathematical models of gas operated small arm jump were developed and used for numerical simulations. Calculated results of jump angle were compared to ones obtained with laboratory stand. Finally, shooting range tests were conducted including precision and dynamic firings. To determine the real jump angle value high speed camera was used. The tests were realized as part of a research and development project No O ROB 0034 03 001 financed by the National Research and Development Centre.
Analysis of In-Bore Balloting and Control of Jump Variability
The variability of the projectile jump is the long-term issue to improve weapon accuracy. However, current simulation code cannot explain explicitly how the variability of jump arises. The aims of this paper are, 1) to give fundamental explanations for the variability of Jump, and 2) to offer design factors to make the variability of Jump less. Objects of the simulation are generic 120mm smooth-bore gun and long-rod projectile system which are regarded as a coupling vibration system composed of tube, sabot, and rod. Analytical formulation and parametric calculations clarified that high Jump-variability is generated only when the last rebound is on the muzzle line. This particular state of rebound is formed by the combination of inputvariables. Guide map named JV-Chart is proposed to show the high Jump-variability.
Limitation of Fire in Automatic Weapon Barrel Due to Thermo-Mechanical Stresses
Automatic weapons are continuously performing their function once the trigger is pressed till the trigger is released. The main characteristic of these is high rate of fire. But, the biggest issue for these weapons is the so-called limitation of fire. There are many limitations of fire, limitation due to increase of thermo-mechanical is my interest. In this paper, limitation due to increase of thermo-mechanical stresses has been analytically and experimentally studied. Some results of the analytical model and experimental study had compared. The same analytical model used to calculate the number of rounds fired before the barrel material reaches its allowable stresses. It was founded that, the weapon theoretically can't reach its limitation of fire due to increase of stresses, but, may be in real the barrel's material characteristics will change by the dramatic change of temperature and it wasn't putted into consideration and it may be the next interest.
Numerical Simulation and Experimental Studies on Weapon Safe Separation for a High Speed Aircraft
One of the key differences between civilian aircraft and military aircraft is its capability to carry and release bombs. From the earliest days of aviation, when the pilot would drop simple bombs by hand, engineers have striven to develop the capability to accurately deliver weapons against targets reliably and safely. The integration of weapons on aircraft requires evaluation of multiple topics related to different disciplines such as aerodynamics, structures, avionics/software maintenance, electro-magnetic interactions, flight test instrumentation, and ground and flight tests. In addition to compatibility concerns, the release of a weapon creates issues such as the ability of the specific store to achieve safe separation and the ability of the aircraft structure to withstand the imparted loads during the ejection of store from pylon or launching phase in the presence of aircraft flow field. The key to a safe and successful store release and its trajectory prediction is to model the separation/ejection process accurately with suitable kinematic and dynamic 3D models that simulate the geometry of store motion from carriage position of the aircraft in a real world application. Present research paper discusses the pit drop tests required for pylon ejector force measurement. Pit drop tests were carried out on an instrumented store, boundary conditions of which are generated to simulate actual release of weapon from a high speed aircraft. The acceleration data thus obtained will be used to carry out safe separation studies on high fidelity aerodynamic models. Paper also discusses the kinematic simulation studies carried out to validate the experimental results.
Simulation Methodology: EM Co-Axial Launcher Using Matlab
EM coaxial launcher is an electromagnetic accelerator. It is a non-contact accelerator thus unconstrained to the speed limit of the intermediate mass. In this launcher thrust is dependent on mutual inductance gradient between the moving and stationary coil. Large acceleration can be achieved but the excitation current must be synchronized with the projectile motion. This paper discusses the theory of operation of EM coaxial launcher and an analytical methodology to calculate magnetic forces between thin coaxial multi-turn coils. The methodology is developed by using filamentary method. To design EM launcher numerical computations are required to meet the desired result. We have discussed various profiles such as force, acceleration and velocity simulated by using mentioned methodology.
Study on the Effect of the Outlet Angle of the First-row Side Holes on Muzzle Flow Field Characteristics
A great amount of powder gas is ejected from the muzzle brake during shooting, which causes great harm to the operators and equipment behind the barrel. Since the energy of propellant gas passing through each row of side holes decreases, investigating the effect of the parameters of the first-row side holes of the muzzle brake on the overpressure behind the barrel is of great significance. Due to the lack of theoretical foundation in the design of baffles behind the first-row side holes, this study focuses on a 125 mm tank gun and a simulation is conducted on the influence of the inclination angle of baffles behind the first-row side holes on muzzle flow field. The simulation is based on Navier-Stokes equations, a high-precision AUSM+ discrete scheme, and a structural dynamic mesh generation technique. The results of the present research can provide reference for the design of the muzzle brake.
Investigation of Influences of Barrel Recoil Velocity on Muzzle Flow Field Characteristics
Research on the flow field around muzzles usually assumes that the barrel is motionless, without considering barrel recoil. The present work studies the influence of gun recoil velocity on the muzzle flow field using computational fluid dynamics (CFD). Using the twodimensional unsteady Navier-Stokes equations, combined with the high-accuracy AUSM+ discretization scheme and a structured dynamic mesh, unsteady numerical simulations are performed for the muzzle flow field including barrel recoil and are compared to experiment. Using the simulation results, the influences of three different barrel recoil velocities on muzzle flow field are analyzed. The results show that barrel recoil causes a reduction in the overpressure in front of the muzzle and increase in the overpressure in the rear area of the muzzle. The magnitude of these effects increases with the recoil velocity. The results of this investigation provide a reference for the design improvement of gun anti-recoil mechanisms.
Research on Influence Regular of Bore Structure Diversification on Band Engraving Resistance
Coupling simulated of classical interior ballistic equations and band's engraving process. A coupled constitutive model considered plasticity and ductile damage effect and based on continuum damage mechanics was introduced to simulate the band's engraving process. The Johnson-Cook hardening model and fracture strain model were used, and the model considered large deformation, high strain-rate, thermal softening and damage evolution, the explicit dynamics algorithm was adopted to simulate the difference of band's engraving processes based on different bore structures. The influence of band's stress state was analyzed based on different bore structures, and the influence regular of band's engraving process dealing with the major structure parameter was pointed out. The results can be further used for integrated analysis and design of guns, ammunitions and propellants for advanced artillery weapon systems.
Numerical Study of Initial Pressure in Unsteady Flow Field with Base Bleed
When the base bleed projectile leaves muzzle, the combustion chambers will undergo a strong unsteady process, which will strongly disturb the tail flow field and affect the drag reduction efficiency. In order to study the effect of the initial pressure on the drag reduction of the base bleed projectile with annular jet during the transient depressurization process, the improved advection upstream splitting method (AUSM+) scheme and k-ω shear stress transport (SST) turbulence model were used to solve two-dimensional axisymmetric Navier-Stokes equations. The development of the flow field at the bottom of the annular jet model during transient depressurization is studied numerically. The characteristic parameters and drag reduction characteristics of the bottom flow field of the annular jet model at different initial pressures are compared and analyzed. The results show that initial pressure has little effect on the flow field structure, and the influence on the flow field characteristic parameters is mainly in 0.1msâ‰¤tâ‰¤1.5ms. The flow field characteristic parameters of the final depressurization process are unaffected. In the process of transient depressurization, as the initial pressure increasing, the bottom flow field spend more time to be stable, the average temperature of bottom decreases, but the average pressure of bottom increases, and drag reduction effect is better.
Numerical Simulation of the In-Bore Motion of a Typical Artillery Shell and Investigation of Balloting
Numerical simulation of projectile motion inside the gun barrel for large calibre gun is a less explored field of study. The projectile behaviour inside the gun is important for both designing of projectile and the gun system. In this study an attempt has been made to model the motion of typical artillery shell in rifled bore of 155mm gun. A 3D finite element model was developed for the rifled barrel and projectile assembly. The simulated muzzle velocity was compared with experimental velocities and appreciable closeness was achieved. To investigate the balloting of the projectile inside the bore, a density-based eccentricity of the centre of gravity was introduced in the projectile. The balloting motion has been clearly demonstrated resulting in engravement on the shell body.
Experimental Studies on Sabot Separation at Intermediate Ballistics
Experimental investigations have been performed on a 25mm sub-caliber projectile in the intermediate ballistics regime. The main objectives were to visualize the flow interactions at the vicinity of the launch tube with the sabot and projectile and prediction of the sabot petal trajectory within the muzzle blast. Sabots with a rear lifting surface have been designed to achieve rapid separation from the projectile using the muzzle blast energy in order to avoid projectile sabot mechanical interaction. Preliminary results show that there is a lifting-up of the sabot in a parallel fashion with respect to the projectile without any mechanical interactions.
Numerical Investigation on the Vertical Water-Entry of a Hollow Cylinder at Low Velocity
Based on the volume of fluid (VOF) multiphase flow equations, the k-ε turbulent model and sliding mesh technique, the low speed vertical water-entry of a hollow cylinder was investigated numerically. The numerical results have a good agreement with corresponding experimental results and finer mesh independence. The results show that a jet flow induced by the through-hole provides a new connection between the inner and outer flow at the pinch-off time underwater. Furthermore, a little bubble on the top of the through-hole jet is created by the collision of the edge surface of the water column inside the cylinder. The initial water-entry speed has a significant influence on the inner cavity formation, the pinch-off depth, the through-hole jet ejection and the motion parameter during the vertical water-entry process.
Study on the Method of Terminal Trajectory to External Ballistics to Terminal Trajectory of Bullet Penetrating Glass
The practical application of bullet penetrating glass is a process of “terminal trajectory to external ballistics to terminal trajectoryâ€ essentially. Based on the overall design of the bullet penetrating glass, the numerical simulation of the bullet penetrating glass, the aerodynamic characteristic analysis, the numerical simulating of the transfiguration bullet penetrating the gelatin are carried out, and the feasibility and rationality of the method are compared with the test in each process. This study found within the speed range the impact of penetration speed on mass loss and length loss was basically the same, 5mm glass has little influence on the stable flight, resistance, the rules of roll change and lethality effect in the gelatin of the bullet can be further analyzed. The movement state of a bullet in the whole process of terminal trajectory to external ballistics to terminal trajectory is analyzed to reveal the motion law of the bullet in this process which can provide technical support for the research and development of high precision ammunition.
On the Study of Automated Identification of Firearms Through Associated Striations
This paper presents possible application of image processing for automatic segmentation of striations and application of machine learning technique for pattern recognition and interpretation of those bullet striations. For identifying the bullet striations an automated technique is proposed. Experimentation was performed on four real test bullets of 5.56 mm calibre fired from two different firearms and two real bullets of 9 mm calibre fired from the same firearm. Experimental results show that it is possible to detect striations from microscopic images of bullets using image processing techniques. Shape features of these striations are computed whose patterns are analysed. Using K-nearest neighbour machine learning technique, we were able to classify firearms correctly with an average accuracy rate of around 84.67%.
Failure Mode Effect and Critically Analysis of Divert Attitude Control System of Launch Vehicle
Divert and Attitude Control System (DACS) is a Liquid Propulsion based Control system, and it is used accurately for positioning the flight vehicle and its payload against disturbing forces. DACS is a very critical system and should have very high reliability. Constant adequate efforts must be made to predict the failures so that it can increase the safety of the system in the detailed design phase by using suitable reliability prediction tools. Failure Mode and Effect Analysis is the best technique to capture the design anomalies/risks systematically. The study of DACS subsystem has carried out with Failure Mode and Effects analysis in a qualitative manner by identifying failure modes followed by tabulating them. Further quantitative Criticality Analysis has carried out, and quantitative risk has been identified. The high-risk components were identified using FMECA, and the associated risk was brought down to an optimum level.
The Analysis of Human-Gun Interaction Process Based on the Functional Near-Infrared Spectroscopy
This study explored the applicability of the human-gun interaction process using the functional near-infrared spectroscopy (fNIRS). The method overcomes the drawbacks of the electroencephalogram (EEG) method that are susceptible to interference by firing. Using fNIRS technique, this study explores the human cognitive characteristics during the shooting of rifle. The concentration of oxyhemoglobin was the analytical indicators for the brain function. It is concluded that: (1) It was obviously regular in time domain characteristics. The five stages were distinguished: raising - aiming - firing - reaiming - reholding. (2)In the spatial characteristics, the cognitive brain activity was mainly related to the orbital prefrontal cortex (OPFC) and rostral prefrontal cortex (PFC). (3)Through calculating Laterality Index, the higher the level of the shooter, the higher the activity of the right hemisphere brain. This study can make an important contribution to human-gun interaction mechanism.
Oblique Penetration of Metal Plates by 25MM APDS-T Projectile—Modeling and Verification
An experimental and numerical research was performed to study the ballistic performance of metal plates subjected to oblique ballistic impact. Even though the oblique homogenous plates are not as weight effective as aluminum/steel and ceramics/steel combinations, they might be a part of effective passive or reactive armor combinations as well as elements of active armor solutions. A secondary objective was to generate verified experimental data for calibration of numerical models. The experiments were conducted using tungsten-alloy (WA) projectile 25mm X 137mm APDS-T. This WA core projectile has high strength and relatively high elongation. Therefore, it is very difficult to bend, break or shutter using oblique impact generating asymmetric forces. In order to find an effective mechanism that will defeat the projectile, it is necessary to develop numerical model that best describes the behavior of the projectile during penetration or perforation of several target plates. To produce such a model it is necessary to conduct ballistic experiments in order to calibrate the projectile’s material model and to model accurately the penetration process into metallic targets having high obliquity.
Analysis of the Effect on the Shock Initiation Performance for Booster Charge Structures Parameters
The booster charge structure has direct influence on the detonation wave propagation, the flayer and shock initiation performance. In order to analyze the influence of the booster charge structure on the performance parameters of the flayer, a numerical calculation scheme was designed based on the orthogonal test principle in view of the three structural parameters, such as the wall thickness of the flying plat, the diameter of the charge and the height of the flyer. The finite difference program Autodyn-3D was used to establish the corresponding numerical simulation model, and the main structural parameters affecting the flyer velocity, momentum, kinetic energy parameters were obtained by the statistical analysis of the numerical simulation results. The analyses and results are significant to provide theoretical basis for the design of this kind of booster charge.
Investigation on the Penetration Performance and Penetration Mechanism of 93W Alloys Fragments
In this work it’s aimed to investigate the penetration performance of three W alloys cylindrical natural fragments that have similar density but different strength and elongation at break. The ballistic impact experiments indicate that the penetration performance of fragments increases with the increase of their strength. The semi-empirical formula for residual mass of W alloys fragments is fitted and it shows that the residual mass increase with the increase of their strength and elongation at break, and the semi-empirical formula can be used as a reference for material design of penetrators with excellent penetration performance. The microstructure analysis shows that the fragments suffer a severe plastic deformation. The failure mode of fragments is plastic deformation failure, and the failure modes of cracks are mainly the cleavage fracture of W particles and the interfacial separation of W particles and bonding phase.
Influence of Intermediate Layers in Reactive Armour Modules on the Protection Capability
Explosive reactive modules can contain low-density foam between the reactive sandwiches in order to prevent sympathetic detonation between the sandwiches. In the present study, the influence of the intermediate material on the protection capability of the ERA modules has been investigated, with special interest on sandwiches with a lightweight rear plate that are designed to give a fast acceleration of the forwards moving plate in order to minimize the length of the precursor. The study showed that introduction of an intermediate material do influence on the protection capability of the armour and that it could be either an overall improvement or deterioration. The mechanisms that have to be balanced are the deceleration of the flyer plates, that decreases the protection capability, and the erosion of the jet tip while penetrating the intermediate material, which improves the protection capability. A simple solution to avoid the deteriorative effect is also discussed.
Numerical and Experimental Study on the Deformation Behavior of 9-MM Parabellum Bullet Impact to the Concrete Target
For shooting scene reconstruction, it has been demonstrated that knowledge about the deformation behavior of bullets can provide beneficial information. In this article, a 3D finite element model of the worldwide-used 9 mm Parabellum bullet impact on the concrete target has been developed with the commercial finite element software, ls-dyna. And the numerical model was validated by the comparison between the numerical and the experimental results. A deformation criteria C was defined to estimate the impact velocity for normal impact events. For oblique impact events, the characteristic parameters, such as the length of bullet, the maximum diameter, the long axis of elliptical interaction zone of bullet with target, the intercept angle between the initial approximate plane of impact and bullet’s axis, are analyzed to evaluate the bullet’s velocity and direction on impact. The calculation suggests that the intercept angle can be used to estimate the impact angle when the impact velocity is not more than the threshold value that leads the cracking of bullets. And the long axis of the elliptical interaction zone is more suitable for evaluating the impact velocity, compared with the bullet’s diameter and length. This study may be significant for shooting scene reconstruction.
Effect of Resin on Laminate Ballistic Performance Subjected to Small and Large Calibre Projectiles
Polymer composite laminates has got crucial role to play in reduction of armour weight due to their high specific energy absorption capabilities. The role of resin in composite armour is paramount in impact energy absorption. In the present study, ballistic performances of E-glass/phenolic and E-glass/epoxy laminates were compared against small arms and large calibre ammunition. The laminates with varying thickness were fabricated through hot pressing method and were evaluated against small and large calibre projectiles. E-glass/phenolic laminate showed 30 % more energy absorption than Eglass/ epoxy laminate. Failure behaviour of laminates were studied and characterized based on delamination and fiber stretching.
Blast Mitigation Study in Composite Materials
Experimental study was conducted to study the effect of low density natural rubber foam and its combination with high density woollen felt layer and aluminum plate on blast wave mitigation. The experiments were conducted using the blast wave generator in three phases with different test configurations. The configuration – I consists of natural rubber foam and woollen felt, the configuration – II consists of different combination of two rubber foam layers with woollen felt layer and configuration – III consists of combination of two rubber foam layers with 2 mm and 4 mm aluminum plates. The blast wave mitigation was measured in terms of the transmitted wave pressure and impulse. The results showed that the transmitted blast wave pressure and impulse decreased with the use of low density rubber foam layers and its combination with woollen felt and aluminum plates. Further, the effect of high density material position in composite was also studied.
Damage Evaluation and Debris Plume Analysis for Spaced Target Under High Velocity Impact Conditions
High velocity impact experiments have been carried out with tungsten alloy projectiles against multiple-plate spaced target configuration using a two stage gas gun facility over a wide range of velocity. The damage on the target layers have been characterized with help of high speed imaging, shock measurements and debris plume analysis. The entry damage diameters have been measured for the target plates and the damage region is defined using damage cone angles. It has been observed that the damage cone angle increases with increase in impact velocity, in general. The entry damage diameter on the first layer remains almost same and that for the second layer increases within a band with the increase in impact velocity for the range of velocity under consideration.
Bumper Efficacy Against Hypervelocity Impact of Projectiles in a Shot Line with Temporal Spacing at High Obliquity
A bumper is an effective shield to protect main structure against hypervelocity impact of a projectile. Its efficacy is mostly investigated for single impact, but inadequately pursued for multiple impacts despite its significance. This may be due to limitations on methodical experimentation. The paper proposes an experimental arrangement for controlled sequential impacts in a shot line for two spherical projectiles (ïƒ† 6 mm) of steel. Impact velocity was around 3 km/s and obliquity was 70ï‚°, 75ï‚° and 80ï‚°. Behind 1 mm thick steel bumper, a stainless steel plate of 1.2 mm thick was kept at a distance of 10 mm as witness. Experiments are simulated in an Eulerian hydro code SPEED and the simulation results are analyzed to investigate effect of temporal spacing on damage to bumper and witness. Projectiles in contact could not perforate witness plate (80ï‚°), whereas temporally spaced projectiles could perforate witness plate.
Design of an Anti-Impact Structure in a Certain Fuze
The fuze installed in the missile withstands all kinds of impact loading during the throw, cutting the shell, explosive separation, etc. The design of an anti-impact structure has been drawing much attention in the fuze field. The fuze under high impact-3000g and frequency- 8000Hz is studied in this paper. Under such strong impact loading, the fuse often breaks down and loses its original function. At first, one protective structure is designed. Secondly, the finite element simulation model is established. Based on this model, the modal analysis is carried out to simulate the natural frequency value. The stresses of the fuze are analyzed under impact loading. The analysis results show that the max stress of the structure is less than the ultimate tensile strength of the material. Thirdly, impact response spectrum experiments are executed and verify that the fuze structure meets the test conditions of environmental impact.
A Comparison on Ballistic Performance of Alumina Segments with Alumina Tiles Using DOP Test Method
Due to increasing requirement for light weight armour solutions the use of ceramic materials in armour applications has enormously increased. However, the multi hit performance of ceramic materials is still a problem due to their inherent brittleness. This problem is generally addressed by changing the design aspect like using ceramic segments instead of tiles. Even though ceramic segments are in use for armour applications for a long time the ballistic performance of these cylindrical segments have not been measured using simple ballistic testing technique like the Depth of Penetration (DOP) test similar to that of tiles. In this study the DOP test method is utilized for ballistic evaluation of cylindrical alumina segments. The post ballistic damage area was found to be lesser in case of cylindrical alumina segments than alumina tiles, but the ballistic performance of cylindrical segments was found to be inferior to that of tiles.
Ballistic Performance of High Strength Steel and Aluminum Plates Against Spherical Tungsten Fragments
This research has shown that great progress has been made in numerical simulations for the perforation problems. The simulations have become reliable and robust, capable of dealing with the complex perforation problems. For the analyses, the material modelling will become a critical issue for the simulation of the performance of some materials. As long as a reasonable material model is provided, the numerical solver are capable of adequately dealing with perforation problems. The study showed that, for example, a very advanced fracture model is needed for the hard metals such as A500T while for 2024-T3 aluminum alloy, even a simple empirical material model will give reasonable results
Comparing Numerical Penetration Modeling of a Monobloc Projectile Into Class B Armor to Empirical Results
The U.S. Army M79 3 inch monobloc projectile was the most basic Armor-piercing round fielded for the M10 Tank Destroyer in WWII. It’s simple geometry and the availability of historical penetration data make it an excellent candidate for comparison of computational models. The M79 projectile impacting Class B armor plates in varying orientations is modeled using the ABAQUS finite element software. Copies of the armor plate were meshed with hexahedral elements in ABAQUS and also with structured tetrahedral elements in Cubit mesh generation software to compare the accuracy of both methods. The calculated limit and impact velocities are compared to the empirical test results previously recorded. The observed results show that the model featuring the hexahedral elements over predicts the ability of the armor plates to arrest the projectiles whereas the structured tetrahedral element model under predicts this. The model accurately replicates empirical results when the there is a significance difference between the striking velocity of the projectile and the semi-empirically derived limit velocity of the plate. At lower velocity differences (under 140 ft/s) the ABAQUS model is far less accurate in matching any comparison metric.
Bullet Penetration into Medium Density Fibreboard Targets
This paper discusses normal projectile impacts on medium density fibreboard (MDF), a wood-based material. Impact experiments have been performed using flat MDF targets. Two different 9 mm projectiles are used, viz. Ball and Ball Subsonic. Penetration depths of projectiles are determined using x-ray photography. The experimental data can be described using both the Robins-Euler model and the Poncelet model. This implies that the resistance to penetration offered by the target can be resolved using two physically interpretable components, viz. the contribution of inertial stresses and the dynamic strength of the material. Results on MDF and wooden targets are compared. For MDF Janka hardness measurements were performed for comparison with natural wood. The observed dynamic strength R shows a good correlation with the Janka hardness. In principle, Janka hardness could be used to predict the resistance of wooden materials to projectile penetration. Finally, possible future research is discussed.
Possibility of Increase in Penetration Depth into Soil and Rocky Targets of Composite Projectiles with the Tail Part Thrown Back During Penetration
The possibility of increase in depth of penetration into soil and rocky targets of composite projectiles with the tail part thrown back in the course of interaction is considered. The thrown back tail ballast mass had a tubular part that acted as a ballistic barrel in which the penetrating module was placed. When the ballast mass is thrown in the direction opposite to the penetration direction, the penetrating module receives an additional impulse in the direction of its movement, which can lead to an increase in the penetration depth of the module. Based on the calculation results, the influence on the penetration depth increase of the mass ratio of the thrown back and penetrating parts of the projectile, of the ballast mass throwing back time, of the throwing pressure and of the ballast mass tubular part length determining the powder gas pressure action time is established for the targets of the type of dense soil and rock.
Assessing the Service Life of Aged Body Amour Products (Helmet-Vest-Insert)
This this study was conducted to investigate the effect ageing/wear has on the penetration capabilities of ballistic vests, inserts and helmets by investigating the ballistic protection capabilities of the worn-out/aged samples (older than 5 years; exceeding the warranty period). The main finding was that worn-out products have constituted failure when tested for their perforation resistance according to NIJ 0108.01 at fair impact velocities. Furthermore, some of worn-out/aged products from the same batch number were re-built by “pressingâ€ as a cost-effective solution to utilize the worn-out/aged body armor products. It was found that “re-pressingâ€ worn-out body armor products increased the ballistic protection capabilities and could be a potential cost-effective solution for wornout/ aged products.
Numerical Simulation on the Penetration Efficiency of Non-Circular Rods
As the increasing impact velocity, the penetration mechanics of non-circular rods has attracted much attention due to its improved flight stability and launch ability. In this paper, the non-circular penetration experiments were conducted to compare with conventional right circular cross-sections. The finite element method using LS-DYNA software was performed to reproduce the penetration process. Penetrators that contain planar elements, such as rods with elliptic, rectangular cross sections are analyzed for the different cases at the impacting velocity of 400m/s~1000m/s. Comparisons are made for equal mass and equal specific kinetic energy penetrators having different cross-sectional geometrics. The predictions of the depth of penetration were validated against the experimental data. Meanwhile, typical failure modes of targets for different non-circular projectiles are investigated in the simulations. The numerical results show distinct advantage of penetration ability for the non-circular rods at higher velocities. The penetration mechanisms between the non-circular projectiles and the targets become different as the change of the stress distribution exerted on the targets. The phenomenon such as self-sharpening is believed to be the major reason for the enhancement of depth of penetration.
Experimentation Using Hot and Cold Steel Plate Targets Against 7.62 x 54RMM B32 API Ammunition
Senf and Rothenhäusler [1] carried out a series of ballistic tests using 7.62 mm ball and Armour Piercing (AP) rounds at three different grades of structural steel over a temperature range of -20 ºC to +80 ºC and at velocities between 700m.s-1 and 850 m.s-1. For all three structural steels tested, they found that, with decreasing temperature, the V50 Ballistic Protection Limit (V50 BPL or V50) increased and, at the temperature extremes, the V50 varied between 20 m.s-1 (~2.5%) to 40 m.s-1 (~5%). This indicates that both the ballistic performance of the target plate is temperature dependent and that this temperature dependence varies with the type of steel. Lynch et al. [2] have previously reported the characterisation of Low Carbon Steels (LCS) at hot and cold temperatures against 7.62 mm Ball. At the time of publication, the 7.62 x 54Rmm B32 API testing had not been completed and could not be reported. This paper continues further with additional 7.62 mm ball and AP ammunition experiments using Hot and Cold targets that were environmentally conditioned at the specific temperature for 24 hours, prior to ballistic evaluation. The steels used were DH36, EH36, S275 and S355 and the target temperatures were Hot (>+50°C), Ambient (~12°C) and Cold (<- 20°C). The target plates were 10 mm thick. This paper completes the data set for the characterisation of LCS at hot and cold temperatures against AP Ammunition to compare with the previously reported ball ammunition experiments. The experimental set was identical with the shots fired horizontally with a 12m stand-off from the end of a remotely operated gun barrel to the front face of the target plate. The targets were placed inside an ISO container (to prevent wind chill, etc. on the conditioned plate firings) and bounded at the rear with 1 tonne sandbags backed with a large Pendine block wall.
Ballistic and Blast Performance of Brick Masonry Walls
Experimental and numerical study of the brick masonry walls to projectile impact and blast loading was performed. The three types of bricks were used: compact, perforated and Porotherm. Concrete and aerated concrete bricks were also used. First, the unreinforced brick masonry walls were tested by the impact of different projectiles according to STANAG 2280. Experiments showed that the walls were resistant to the projectile impact on level A3. In order to increase of the walls ballistic performance some reinforcement of the walls were suggested. This reinforcement which was realized using of some add-on plates made from basalt and ceramics leads to the increase in the ballistic performance of the brick walls from level A3 to level A4. In the next step brick unreinforced masonry walls were tested under blast loads generated by the explosion of 10 kg and 20 kg of TNT charges at the distance of 1.5 –5 m from the wall. The numerical simulation was used for the evaluation of the effect of material strength, boundary conditions, and thickness of the wall on the blast response of both reinforced and unreinforced brick masonry walls as well as on the masonry walls response to the projectile impact.
Numerical Simulation of Ballistic Impact on Different Types of Helmets
The paper deals with numerical simulation of the response of the three types of helmets (combat helmets, helmets for military policeman and helmet for the paratroopers) to ballistic impact by the fragment simulating projectile (1.1 g). All tested helmets were made from aramid laminate. The geometry of the helmets was obtained using 3D scanning and following smoothing. The simulations of the frontal, side and back impacts of the fragment-simulating projectile (FSP) were carried out using LS-DYNA. As a ballistic limit V50 was taken the fragment striking velocity when 90% of layers were damaged. The simulation results showed that ballistic performance of the helmet is affected namely by the impact point position.
Using of Fluoropolymer Materials to Defeat Lightly Armored and Easily Vulnerable Targets
The article deals with the possibility of increasing the damaging effects of small-caliber artillery ammunition in the fuel tanks of aircraft and helicopters. A comparison of the results of the calculation of the probability of the incendiary effect of strikers based on fluoropolymers on diesel fuel was made. The calculations were carried out using the methods of “Fragment Criterionâ€ and “Energy Balanceâ€.
Experimental Study on the Performance of Projectiles Penetrating Multilayer Laminated Glass
Study on the mechanical properties and protective mechanism of multi-layer laminated glass under the penetration of 7.62mm rifle bullet. Comparison on the effects of different thickness polycarbonate PC and glass on the ballistic glass anti-elasticity by the experimental study on the penetration of laminated glass by 7.62mm rifle bullet. Meanwhile analysis the lightweight of bulletproof glass. The results show the PC material can effectively improve the performance of bulletproof glass with the same quality. The front PC can effectively suppress crack propagation and prevent extensive damage to the glass and the crater is smaller. The more layer in the number of bulletproof glass is beneficial to its anti-ballistic effect.
Research on the Penetration Law of Jet to High-Speed Thick-Wall Ammunition
An attack model of shaped charge warhead against attacking high-speed thick-wall ammunition is proposed in this paper. For the problem of shaped charge jets penetration high-speed moving target, through the analysis of the whole penetrating process between the shaped charge jet and the thick moving target, based on virtual origin theory. In order to verify the theoretical model, we designed three typical shaped charges, and LS-dyna finite element software was used to analyze the penetration process of jet penetrating thick-walled target at different velocities. The results show that the theoretical model established in this paper can accurately calculate the motion state of the jet element in each stage, thus obtaining the rule that the total
Dynamic Back Face Deformation of a Combat Helmet Upon Oblique Impact of a 7.62X39 MM PS Projectile
Body armour is the only protection a dismounted soldier has against the 7.62x39 mm rifle projectile threat. While body armour protects against such threats, weight limitations challenge helmet manufacturers to make a helmet withstand a direct rifle projectile impact. However, an oblique projectile impact on a helmet has the highest probability. This work promotes the 7.62x39 mm projectile ricochet off helmets to increase the likelihood of projectile deflection and the survivability of the wearer. Also, a deflected projectile causes severe deformation on the helmet shell. Optical measurement systems capture the deformation, and this data is transferred to numerical models. Numerically achieved BFD data in a LS-DYNA® Finite element (FE) head model is used to evaluate the blunt trauma using a head injury criteria (HIC) in the advanced SUFEHM model.
Comparative Analysis of Arbitrary Lagrange in Eulerian (ALE) and Adaptive Smooth Particles Hydrodynamic (SPH) Simulation of Rocket Propelled Grenade (RPG) on Armors
Military ground vehicles and helicopters are vulnerable to buried landmines, Improvised Explosive Devices (IED) and unguided ground launched threats particularly, the RPG-7 Rocket Propelled Grenade. Detonating IED’s and landmines creates a blast pressure and propagating blast waves near the ground vehicles causing both structural damage and crew injuries. On the other hand, projectiles and RPG’s cause the structural damage and crew injuries by their impacting velocities. RPG-7 with a top speed of 294 meters per second (660 mph), strikes the target with a velocity in excess of 1100 meters per second (2460 miles per hour) with its jet tip speed and pierces up to 400 mm of Rolled Homogenous Armor (RHA) steel. High penetration of RPG’s with a shaped charge is a big problem to protect against and to simulate. Arbitrary Lagrange in Eulerian (ALE) method of simulation is well suited for large deformation blast problems. In this study, two simulation methods of RPG are compared, namely ALE and ALE coupled with adaptive Smooth Particle Hydrodynamics (SPH). In order to capture the jet tip formation and slug formation with high degree of accuracy, it is necessary to model the RPG threat with fine details. It is also necessary to model the vehicle platform and the RPG in detail to understand better and quantify its impacting on engagement. There are many probabilistic models available to predict the chances, but they don’t capture the accuracy. The simulation method addressed in this study aims at capturing the armor response with high accuracy on RPG impact and engagement. To perform these analysis, LSDYNA based ALE and ALE-SPH (3D) methods were used. This will enable us to understand the RPG threat better and the effectiveness of the impact on the target, and helps to develop a suitable defeating mechanism and mitigating solutions
Research on Bearing Ball Impact on Flat Glass
In order to research on the phenomenon of damage and fracture cause by BB(Bearing Ball) impact on flat glass, numerical calculated model is established with finite element software, the penetrated effect of BB with different velocity impact on flat glass was simulated, combined with the experimental data, the fracture and failure wave produced in flat glass is discussed. The calculated fracture feature of glass coincides with result of experiment, numerical simulation illustrated the crack development in flat glass. The research shows that, along with the BB’s velocity increasing, the diameter of punched hole and the area of spall is increased no longer, the lens area in fracture surface disappeared, the fog area in fracture surface increased; when the impact pressure in glass is between 0.5~0.9 HEL s , the velocity of failure wave which generated in flat glass is approximately 3.3km/s, the failure wave is generated earlier due to the impact velocity increase.
Resistance of Steel–Elastomer Laminate Armors to Impacts of Small–Caliber Projectiles
Monolithic, homogenous ballistic shields consisting of a single thick, high-hardness and high-strength steel plate are rarely applied in modern combat vehicles. Nowadays, multilayered laminates are a popular armor solution due to which the threat kinetic energy is dissipated by a complementary performance of components with different material properties. Searching for a maximum ballistic protection results in applications of various materials assembled together to provide an improved protective efficiency without excessive mass. The presented experimental investigation focuses on a steel–elastomer armor concept and aims to verify the influence of the elastomeric interlayer on the behavior of the laminated shield under impacts of small–caliber 7.62×54 R API B32 projectiles.
Defeating EFP Threats by Metallic Plates—A Parametric Study Through Numerical Simulations
One of the most lethal threats to armored vehicle is the explosively formed projectile (EFP), which is launched by a relatively simple explosive device. These compact metallic projectiles can reach velocities in excess of 2 km/s and have a high penetration capability, which can results in significant damage to the interior of the vehicle. The common armor against this threat is comprised of several plates which serve to deform and decelerate it, so that it will not penetrate the vehicle's wall. In the present study we used numerical simulations in order to follow the interaction between a short copper projectile with a relatively thin metallic plate, as a function of the mechanical and physical properties of the plate material. We focused on the projectile's deformation and its deceleration, as they affect its ability to penetrate a distant witness block. The properties of the plate material which we varied systematically in the simulations, include its compressive strength and failure, as well as its density. We also examined the influence of a moving plate's relative velocity on the projectile's residual penetration.
Explosive Induced Shock Attenuation in Teflon— An Experimental Investigation
Shockwave attenuation characteristics of polymeric materials are important to be known for designing waveshapers. Waveshaper in shaped charge enhances its penetration performance by suitably altering the detonation wave interaction with liner surface. An optimized wave shaper geometry with appropriate material results in low warhead weight and less space requirement with enhanced penetration capabilities as compared to point initiated charge. The geometry of wave shaper is dependent on shock behavior of its material under explosive loading. Optimized configuration of wave shaper can be arrived at by knowing the shock characteristics of its material when it is loaded with same composition and quantity of explosive as in the warhead configuration. Teflon is one of the candidate materials for wave shaper due to its advantages of low density, machinability, dimensional accuracy, faster shock attenuation, availability etc. This paper discusses experimental and numerical simulation approach to determine shock behavior of Teflon material under explosive loading. Shock attenuation properties obtained from experiments can be used for design of a wave shaper for shaped charge application.
Perforation of Medium Thickness Metal Plate by Flat-Nosed Projectile
A model of flat-nosed projectile perforating medium thickness metal plate at normal incidence is proposed in this paper. The perforation process of metal plate is divided into three phases: transient impact phase, penetration phase and plugging phase. In transient impact phase, different regions are divided and the end time of this stage is calculated according to the propagation of shock wave and rarefaction wave; In penetration phase, by calculating whether the projectile has head deformation region, it can be divided into two different cases. The length of deformation region is dependent on the velocity of projectile, the penetration velocity and the plastic wave propagation velocity; In plugging phase, the plugging failure of the plate is connected with an adiabatic shearing process. Moreover, the effect of the entrance phase is analyzed by using finite element software and taken into account in this model. The calculated results of the theoretical model are in good agreement with the experimental data.
Jet Formation Theory of Hyper-Cumulation Charge with Additional Body
The Russia scholar Minin has proposed that the shaped charge with additional body (Addbody) called hyper-cumulation charge (HCC) can form a jet called hyper-cumulation jet (HCJ) with higher velocity and mass. In this work, a theoretical model for calculating the velocity and mass of HCJ is presented, which shows the relationship between the characteristics of the HCJ and the parameters of the structure of HCC as well as the material, including the thickness, density, diameter, and cone angle of the Add-body and truncated liner. A series of numerical simulations of the HCJs are carried out by changing the density of the Add-body. The results are compared with the theoretical calculations and they are in good agreement. It can be concluded that in this work, when the density of the Add-body is about 12000kg/m3, the HCC can form a better HCJ with the tip velocity of 8673m/s, 1400m/s larger than the traditional shaped charge jet (SCJ), and the model can greatly predict the HCJ formation process and provides a quantitative design method for HCC.
A Simulation Model for Computation of Safety Distances of Artillery Guns Based on Casualty Criteria
Artillery guns firings in offensive mode may lead to friendly casualties. It is amongst these firings that safety distance based on acceptable casualty criteria is defined so as to facilitate our own troop movement. The distances, up to which our own troops can move without any casualty or say, some acceptable percentage casualty is of utmost importance at the time of planning and operationalizing movement of troops. Movement of personnel towards the target can be visualized from two directions – along the line of firing and perpendicular to the line of firing.These safety distances depend upon characteristics of weapon, ammunition, fuze being used and direction of movement of troops. A simulation model based new methodology is presented in this paper which takes in to account all parameters involved viz., range, dispersion, terminal velocity of shell, angle of descent of shell, point of burst, experimental mass and spatial distribution of fragments and terminal velocity of fragments. The model is programmed and implemented in MATLAB® and results are validated with experimental values
Ballistic Impact Analysis of Combat Helmet on a Human Head Surrogate Using 3D-DIC
With the widespread use of combat helmets, behind helmet blunt trauma (BHBT) has emerged as a serious injury type experienced by soldiers. In the current study, a synchronous test system was constructed to study the pistol bullet penetrating into combat helmet covered human head surrogate. The 3D digital image correlation (DIC) method was used to directly measure the characteristics of the dynamic front face deformation at impact area of helmet. The shape and size of the front face deformation time histories, deformation velocity, and line slices profile on helmet surface were obtained. The pressure sensor was mounted in the center of the head surrogate and was buried in the clay. The time histories of the impact pressure of the two sets of tests were captured. These results could then be used to develop new combat helmet.
Mechanism of Multi-Layered Fragment Separation Due to High Explosive Loading
In a multi-layered, pre-made fragment warhead, the interaction between the detonation waves from the explosive and the pre-made metal fragments results in the separation of the fragments from each other. This paper aims at understanding the mechanism behind the multi-layered fragment separation by studying the propagation of shock waves through the fragments and taking into account the finite strength of the fragments at such high strain rates. By analyzing the forces that act on the fragments, we can better understand the role of the different forces that act on the fragments. A numerical approach is used to simulate the multi-layered fragment separation using spherical fragments keeping the C/M ratio constant. A single column of fragments is modelled and simulated for 2, 3, 5 and 7 layers of fragments.
Impact Response of A 50 MM Thick Rolled Homogeneous Armour Against 40 MM Armour Piercing Shots: An Experimental Study
Ballistic performance of a 50 mm thick rolled homogeneous armour plate by impacting 40 mm armour piercing shots is evaluated through high speed shadowgraph experiments. The shots were impacted at 0° angle of attack with the plate. Perforation and deformation of the plate at the impact site was investigated at every 20 μs interval through high speed shadowgraph experiments. The impact events were illuminated using suitable arrangements of flash bulb illumination. During the test, performance of the plate was investigated for different striking velocities (vs) ranging between 546-789 m/s. Our results show that the shot gets shattered at a striking velocity of 756 m/s. Further increase in striking velocities results more number of flying fragments at the exit end. Investigation on bulge formation on rear side of the plate during shot-armour interaction reveals that height of bulge (hb) before its tearing increases with increase in the velocity and attains a maximum and then decreases for higher velocities where shot shattering occurs.
Estimating Primary Fragment Characteristics During Hypervelocity Impact of Spherical Fragment on Thin Plate Using Artificial Neural Network
A complex phenomenon of hypervelocity impact shows changing trends in plate damage for range of impact condition. Empirical models predict damage in terms of hole size and characteristics of residual projectile, which is detrimental to cause further damage of next layer plate. In the present work, an attempt is made to develop artificial neural network (ANN) for predicting the characteristics of residual projectile in terms of mass ratio, velocity ratio and obliquity. The ANN predictions were compared with results obtained by simulations with were validated with experimental results in the literature. It is observed that predictions done by ANN are in good agreement with simulation results.
Ignition and Breakup Behavior of Fuel Tank by Reactive Material Fragment
Combined studies on the behavior of reactive material fragment damaging fuel tank are performed, experimentally and theoretically. Firstly, ballistic experiments on reactive material fragment impacting and igniting fuel tank are conducted. The results show the reactive material fragment with the velocity above 732m/s can perforate the LY12 aluminum wall 10mm thick and then ignites the fuel/air mixture inside, causing breakup of fuel tank. However, the tungsten alloy fragment mass matched fails to ignite the fuel at a velocity of 933m/s. Secondly, the ignition enhancement behavior is analyzed and discussed, based on a fracture model of reactive materials and a fuel/air ignition model. For the mechanism considerations, traditional inert fragment emphasizes on the kinetic energy effect. However, reactive material fragment enhances lethality by incorporating the terminal defeat mechanisms of kinetic energy and chemical energy, and the convective heat conduction between reacting reactive materials and fuel/air mixture is the main ignition mechanism.
Numerical Simulation of Anti-Penetration Performance of Liquid Composite Armor to Shaped Charge Jet
Focusing on the characteristics that liquid can effectively interfere with jet stability, scholars have gradually carried out research on the liquid-filled composite armor.
Controlled Fragmentation Warhead for UAVApplications
This paper presents theoretical assessment of controlled fragmentation (CF) warhead and its application for (Unmanned Aerial Vehicle) UAV. It is a great challenge to the designer to make small warheads with precision for defeat ofground targets. Attempts have been made to optimize the performance parameters of small warheads to be used in UAVs for defeat of specified ground targets. Warhead performance parameters are characterized by mass distribution and special distribution, velocity of fragments and penetration performance of fragmets against ground targets. Lethality of warhead depends on explosive filling, case materials and controlled fragmentation techniques. Parametric studies are carried out to improve the performance parameters in the best possible manner. The theoretical model shows that the warheads in the weight class of 1kg can defeat simulated targets of 5-mm thick mild steel at a lethal radius of 10m, generating more than 250 numbers of 1 to 2-g compact fragments in beam angles of the range of 100-120.To check out the efficacy and effectiveness, two cylindrical warhead prototypes using controlled fragmentation were fabricated and tested in similar conditions.
Numerical Investigation on the Impact Response of Rolled Homogeneous Armor (RHA) with Spall Liners
The armor, on impact by a projectile, not only is pierced, but also generate debris which are known as spall. Liners are generally used to decrease the lethality of spall and increase the survivability of personal. The present numerical study investigates the spall generated by impact of an Explosively Formed Projectile (EFP) and Shaped Charge Jet (SCJ) on Rolled Homogeneous Armor (RHA). In the first part, the RHA was modeled using SPH method and different failure models were used to determine the spall parameters on impact by EFP. In the second part of the study, a series of simulations were performed to characterize the performance of liner materials (mono layer and multi-layer) and configurations in reducing spall generated by impact of EFP and SCJ. The introduction of liners greatly reduces the lethality of spall and the principle mechanisms aiding performance were identified. Liner performance is greatly dependent on the areal density, compressibility and strength of the materials used
High Strain Rate Behavior of Steel Material Typically Used in Armour Applications
Materials behave differently when subjected to loads at different strain rates. The study of this field is very important in the analysis of the behavior and failure of components and structures that are subjected to dynamic loads. In the present work, the high strain rate behavior of steel used in armour applications has been investigated through tensile tests at low and medium strain rates and high rate compression tests in SHPB set up. The study shows that the material exhibits moderate strain rate sensitivity and is fairly constant over a wide range of strain rates.
Ballistic Impact Damage and Fragmentation in Different Types of Glass and Glass Ceramic
Different types of glass and glass ceramic, including Supremax®, Pyrex® and N-BK7 optical glass, were impacted in a normal ballistic arrangement with 7.62 mm armor piercing (AP) projectiles and with solid steel cylinders at 830 m/s. The plates were integrated into a target box, which allowed for an almost complete recovery and analysis of the glass fragments. Different types of high-speed cameras were used in order to visualize the different phases of fragment formation and ejection. The glass and glass ceramic fragments were extracted from the target box and separated into size classes by a chain of sieves. The mesh sizes used were 2 mm, 1 mm, 0.5 mm, 200 μm, 100 μm, 63 μm and 25 μm. The total mass of each size fraction was determined. The single crack velocities and damage propagation velocities were determined from the high-speed photographs for all materials
Study on the Forming Performance of Central Perforated EFP Warhead
The central perforated EFP warhead was usually used in the terminal sensitive projectiles because of the compact structural configuration requirements. In this paper, the influence of this structure on the forming processes of EFP was studied and discussed. The EFP forming process of the central perforated liner and the traditional hemispherical liner were numerically simulated respectively by Autodyn software. The head velocity and lengthdiameter ratio of both EFPs were compared and analyzed. Secondly, the influence of circular initiation mode on the EFP forming performance was studied. The numerical results shown that the larger the radius of circular initiation, the larger the EFP aspect ratio and the higher the overall EFP speed.
Empirical Equation for the V50 Velocity of Small Arms Armour Piercing Rounds Onto Armour Steel
This paper describes an empirical model for estimating the ballistic limit of a small arms armour piercing projectile with a hard steel core against a steel target. The input variables are steel thickness and hardness, projectile core diameter and mass as well as the obliquity of impact. The model constants were found by nonlinear curve fitting against a set of 98 data points found in literature. The model was able to reproduce the results with a standard deviation of the absolute error of 5.8 %. To further validate the model, ballistic tests were performed with two small arms AP projectiles not included in the model optimisation against two steel types. The model was able to estimate these four new experimental data points with a standard deviation of the absolute error of 7.3 %. This supports the usefulness of the model for armour and test design.
Hypervelocity Oblique Impact of Spherical Projectile on Thin Walled Targets
Angle made by the axis of spherical projectile with the normal to the surface of the target is called angle of obliquity. The angle of obliquity at which the projectile rebounds or moves off the target is called critical ricochet angle and this phenomenon is termed as ricochet. In the present paper the phenomena of ricochet is studied under velocities such as 1 km/s 2 km/s and 3 km/s, considering targets of thicknesses 1mm, 3mm and 5mm with projectile of 6mm diameter. ANSYS Autodyn is used for numerical simulation of impact event. The strength and damage characteristics are inculcated using Johnson Cook material and failure models. Some interesting observations are made which will be discussed further with the help of graphs plotted using MATLAB. Lagrangian mesh with adaptive meshing is considered to capture the information precisely during excessive deformation.
Study of Polyurea Application in Ceramic Armour Module Against Long Rod Projectile
An experimental study was conducted to investigate the potential application of polyurea in a ceramic armour against long rod projectiles. The Dragonshield-BC polyurea was used in this study. The baseline armour module configuration consisted of a 5 mm thick steel cover plate, 20 mm thick SiC tile and 10 mm thick steel backing plate. The layer of polyurea was added either between the cover plate and ceramic or behind the backing plate. The armour modules were subjected to normal impact by tungsten alloy long rod projectiles at a nominal impact velocity of 1.25 km/s. A witness block made of AISI 4340 steel was placed behind the armour module to capture the residual projectile. Armour module performance was assessed using mass efficiency. This study revealed that polyurea enhanced cover plate could improve ceramic armour performance depending on configuration. The four configurations were: (1) 2 mm thick polyurea bonded to cover plate, (2) 4 mm thick polyurea bonded to cover plate, (3) 2 mm polyurea interlayer without bonding with cover plate and, (4) 2 mm polyurea bonded to 2 mm thick cover plate. Of the four configurations tested, only one showed at least 45% improvement in mass efficiency while the rest had little or no effect.
A Unified Formula of Critical Penetration Velocity for Natural and Preformed Fragments Penetrating Into Steel Target
Using dimensional analysis method, a unified formula of ballistic limit velocity for natural fragments and preformed fragments penetrating into steel plate was established. The penetrations of natural fragments, spherical preformed fragments, cylindrical preformed fragments and cuboid preformed fragments into steel plates were studied by means of experiments. After the data processing of the test results, the empirical constants in the unified formula was obtained. The predicted results by use of the unified formula are in good agreement with the experimental results
Ricochet and Fragmentation Analysis of Projectile from Impact on Steel Plate and Soil Using Numerical Simulation
Determination of Surface Danger Zones (SDZs) is a safety related issue of paramount importance which must be addressed. Several technical factors are involved in SDZs determination for a specific weapon and ammunition system: range of fire, dispersion, ricochet and fragmentation. This work is focused on the ricochet and fragmentation of 120 mm typical training round tank ammunition during high velocity impact. The modeling is based on numerical simulation for analyzing the large deformation dynamic response of the round structure during impact. The main aim of the numerical analysis was to examine the various impact parameters of the ricochet i.e. the critical angle for penetration or fragmentation and to understand the effect of the impacted surface properties on the ricochet behavior. The numerical model presented was calibrated and compered to ricochet firing test that included 120 mm tank training round fired against hard armored steel, and soft soil targets.
Analysis of the Impact Velocity Effect on the Parameters of the Brownian Motion Based Approach for Ballistic Resistance Estimation
One main challenge in ballistic protection development is the performance evaluation and assessment of the final product. Three metrics are used for that goal: the perforation/no perforation observation, the residual velocity or the depth of penetration measurements. Different methods have been introduced over the years for measurements processing and ballistic perforation evaluation. Recently, a stochastic approach based on the Brownian motion process has been proposed where the model parameters (the bullet deceleration and the diffusion coefficient) have been assumed constant. The goal of the present work is to analyze the effect of the bullet impact velocity on the model's parameters. The model's parameters dependence on the bullet initial velocity may improve the model fitting to experimental results due to its direct influence on the bullet deceleration during the penetration phenomenon.
An Investigation of Armor Bolt Failure Due to Ballistic Events
The US Army is interested in better predicting failure under impact of the bolts that attach armors to vehicles or the main armor. To understand the forces and failure process, the Army started systematic experimental studies where bolt torque, number of plates, plate materials, etc. were varied to measure the force the bolts had to support for different configurations. A computer simulation effort was initiated and presented in the last International Symposium on Ballistics to determine the Johnson-Cook (JC) constants of the bolt material. The objective of the present work is to validate the constants obtained there by comparing the forces measured in the laboratory tests by Klann with the ones computed using LS-DYNA and EPIC. This paper describes the computer models for the armors of interest as well as some details on boundary conditions, material models, and validation studies. It also presents parametric studies. When possible, the computations are compared to test results.
Experimental Study on the Effect of Head Cone Angle on the Low Velocity Oblique Inlet Process of Projectile
In order to study the influence of the head cone angle and velocity of truncated cone-shaped projectiles on the cavitation and trajectory characteristics under the condition of low-speed oblique entry into water, based on the high-speed camera method, the comparative experiments of different truncated cone-shaped projectiles at low-speed oblique entry into water were carried out, and the effects of the head cone angle and velocity of truncated cone-shaped projectiles on the entry cavitation, movement speed and pitch angle were obtained. The experimental results show that the smaller the cone angle of the truncated cone projectile's head, the earlier the tail collides with the lower wall of the bubble. The smaller the head cone angle is, the faster the initial velocity is, and the later the time of deep closure of the cavitation is. The cavitation of the projectile increases with the decrease of the head cone angle and the increase of the velocity. Velocity and head cone angle have influence on the stability of water inflow. When the velocity of projectile is lower than the critical value, it tends to increase, and when it is higher than the critical value, it tends to decrease.
Modeling on the Shock Wave in Spheres Hypervelocity Impact on Flat Plates
To estimate the geometric features of the wave front during the first complete propagation in the spherical-projectile, the Geometric Propagation Model (GPM) is built in this paper to describe the geometry of the shock wave front, which proposes an ellipse contour as a function of time and equivalent speed. The GPM identifies the geometric features of the wave front as a function of time and impact velocity successfully. Meanwhile, the attenuation of shock amplitude and peak pressure in the projectile is also analyzed with the GPM and simulations. The GPM may be applicable to hypervelocity events involving any monolithic materials as long as the equivalent speed could be supplied from theoretical calculation or numerical simulation.
Target Flow Fields and Penetration Resistance for Pointed Projectiles
Methods for determining target resistance using velocity fields have been very successful for hemispherical-nosed and eroding projectiles which produce a hemispherical flow. Pointed-projectile-induced target flow fields are more challenging due to the pointed nose itself being a singular point in the flow. This paper develops a flow field, based on the curl of a vector potential, that produces a singular flow field for pointed projectiles (including ogives and cones) and produces target resistances through integrating plastic work rates over the flow field. To give an example of the utility of these new flow fields and target resistances, comparisons are made using the new flow field in the Walker-Anderson model for ogival-nosed APM2 projectile ballistic limits and deep penetration. Agreement is excellent.
Firm Embedding Behavior of Annular Grooved Projectiles Impacting Ductile Metal Targets
Annular grooved projectiles (AGPs) have drawn ongoing concerns as an advanced penetrator for their excellent anti-rebound capability in impacting metal plates. They could become embedded solidly in the target surface during low-velocity impact. In this investigation, the firm embedding behavior of AGP was observed by impact experiments. Corresponding numerical simulations provided an better understanding of this process. Experimental and numerical results indicated that the firm embedment behavior of the projectile was mainly due to the filling-material in the groove rather than the friction between the projectile and target. According to observation, firm embedding process can generally be subdivided into four stages: initial-cratering stage, groove-filling stage, fillingmaterial failure stage and rebound vibration stage. Moreover, the damage mechanics of target material around crater was obtained through microscopic tests. A comparison of the cross-sectional figures between the experiment and simulation proved that the analysis and the proposed method were reasonable and feasible.
Thin Flyer Impact Initiation Study of Ultrafine CL-20/HMX Co-Crystal Explosive by Varying Barrel Diameter
Hexanitrohexaazaisowurtzitane (CL-20) is one of the most powerful explosive materials with potential for development of futuristic miniaturized high performance devices. It has small critical diameter which make it suitable to be initiated by short duration impact generated by small diameter and thin flyer in exploding foil initiators. However, the use of this material is limited due high mechanical sensitivity that strongly influences the safety of a formulation. Therefore, there is a need to improve the sensitivity of CL-20 explosive without compromising in explosive performance. Recently co-crystallization concept has evolved to get the desired insensitivity. In this research work, a new recrystallization method using twin fluid nozzle spray system has been established for making co-crystal of CL-20/HMX (2:1). The explosive co-crystals obtained by this process was characterized and analyzed using particle size analyzer, surface area analyzer, FTIR, FE SEM, X ray diffraction and thermal analytical techniques. It is confirmed the formation of co-crystals and showed that the prepared sample is not a physical mix of CL-20 and HMX. FE SEM analysis showed the particles formed are in the range of 2-5 μm and composed of numerous thin plates of thickness approximately 100 nm. Prototypes of exploding foil initiators using co-crystal of CL-20/HMX explosive were fabricated and the performance was evaluated. Threshold initiation studies were conducted using Bruceton sensitivity test with varying barrel diameter of 0.3 mm, 0.5 mm, 0.9 mm, keeping other parameters same. It was observed that the exploding foil initiators with barrel diameter 0.3mm did not function even at higher voltage and the threshold voltage with barrel diameter 0.5 mm was found to be lower than that of 0.9 mm barrel. It was experimentally found that the barrel diameter has significant effect on threshold voltage as the threshold voltage is reduced by 33% by optimizing barrel diameter from 0.9 mm to 0.5 mm.
Re-Visiting the Mass-Flux Model for Explosive Reactive Armor and the Effect of Plate Thickness
Explosive Reactive Armor (ERA) is usually composed of an explosive layer in between two steel plates. The plate that is being hit first moves towards the jet and is called the Backward Moving Plate (BMP). The second plate moves with the jet direction and is therefore named the Forward Moving Plate (FMP). In 1984, the first theoretical paper explaining the mechanisms by which ERA defeats shaped-charge jets was presented [1]. The paper revealed several physical mechanisms for the first time, including the hydrodynamic mass-flux model. Since each plate has a different velocity relative to the incoming jet, the interaction time interval and velocity between each jet element and plate, is different. As soon as the jet tip hits the cassette, the explosive is detonated, causing the metallic plates to move aside and disrupt the jet. The plates' velocity is usually one order of magnitude lower than that of the tip of the jet, and since the jet is usually thin, the craters created in the plates during the sideways interaction are also small, causing long, thin craters in the plates which were named “stripsâ€. It was therefore hypothesized that the interaction between the main part of the jet and the plates could be regarded as an interaction between two streams: the jet and the strip. The massflux ratio of the two will determine the ERA effectiveness. A detailed consideration of the mass-flux distribution of the jet throughout the entire interaction process was missing. The present work will describe this distribution, and address the benefits for the ERA effectiveness that are formed by the plate thickness. Moving from jet tip to tail (excluding the tip itself, the appendix, and the slug), the jet velocity decreases while its diameter increases. The distribution of the massflux of the jet emerging from a 60º point initiation charge [6] computed by the MSCAN code (for a mass-flux arriving at a fixed target)[8] is presented in Fig. 1. This mass-flux consideration overlooks two main problems, which are solved differently.
High Strain Rate Deformation Behavior of Materials: Effect of Crystal Structure, Grain Size, Microstructure and Texture
Various materials are being subjected to high strain rate loading conditions when in use such as penetrator or armour. Armco Fe, Pure Mg, Ultra high strength martensitic steels are some of the widely used material. However, limited study exists on understanding effect of crystal structure, strain rate and temperature dependent deformation behavior of these materials. In the current study, we explore the strain rate and crystal structure dependent change in deformation mechanism of these materials. Pure Mg and Fe were subjected to compression at a strain rate of 0.01- 4000/s. The effect of strain rate, initial microstructure and texture on twin induced grain re-orientation, slip and twin-slip interaction is studied. An approach to derive a physics based model to depict microstructure based phenomenon is discussed. The effect of strain rate on flow behaviour and fracture in Ultra High Strength martensitic steels along with adiabatic shear band formation is also explored.
Simulation Study on Dynamic Response Characteristics of Projectile-Borne Recorder Under Impact Loading
Dynamic finite element simulation models of two projectile-borne recorder structures with different natural frequencies are established. The dynamic response characteristics with different elastic modulus of buffer materials under different pulse width of half sinusoidal signals impact loading are analyzed. The simulation results show that the acceleration peak value decreases with the increasing of elastic modulus of buffer under low frequency loading, which is contrary to under high frequency loading. And it increases firstly and then decreases with the increase of loading frequency, which is opposite in different loading frequency bands for two structures. The acceleration peak value of circuit component with low natural frequency is larger than that with high natural frequency when a half sinusoidal signal acts with low frequency, which is contrary to that with high frequency
Effectiveness of Different Shear Thickening Fluids in Reducing Back Face Signature (BFS) of Body Armor Against Bullet Impact
Shear thickening fluid (STF) or liquid armor based flexible & light weight liquid armor is attraction for both defense and Civilians. In order to understand the contribution of shear thickening behavior on ballistic performance of STF coated Kevlar fabrics, STFs of different shear thickening behavior were prepared by varying the particle size (100- 1000nm) and concentrations (62-70%) of nanoparticles in polyethylene glycol matrix. STFs were coated on Kevlar fabrics using Mathis padding mangle. Ballistic Trials on STF Coated Kevlar fabrics were performed as per NIJ level IIIA using 9mm x19mm ammunition with projectile mass 7.45 g and velocity 430±15 m/s respectively. Roma Plastilina #1 is used as backing material for the measurement of Back Face Signature (BFS). It was observed that BFS reduced significantly with STF coating on Kevlar fabric irrespective of rheological parameters. BFS does not show significant difference for particle size 100-600nm and performance suddenly falls with further increase in particle size. It is further observed in present study that STF coating on Kevlar fabric shows improvement only up to an optimum concentration, beyond which there is decline in performance.
Trajectory and Loads for Oblique Penetration Into Concrete Targets by Rigid Projectile
This paper studies the trajectories and loads of rigid projectiles penetrating into concrete targets with oblique and attack angles, based on differential area force law with an empirical model of free surface effect. Investigations are conducted using 450kg, 300-mm-diameter ogive-nose projectiles, with striking velocities from 600 to 1000m/s, oblique angles from 5° to 25° and attack angles from 1° to 5°. The characteristics of trajectories and loads are summarized. An important characteristic is that the turning of trajectory direction only happens at the earlier stage of penetration, and then the trajectory converge to straight line and keep linear motion until the end. Consistent with the trajectory, the attack angle, lateral acceleration and moment all occur at this stage. The axial acceleration is mainly determined by the initial velocity, but the lateral acceleration and moment are determined not only by initial velocity but also by the initial oblique and/or attack angles. In terms of maximum loads of lateral acceleration and moment, the combined influence of initial oblique and attack angles is larger than a single factor. There exist a proper negative attack angle which can minimize the trajectory turning in oblique penetration cases
Experimental Study on the Characteristics of Liquid Spurt Caused by Hydrodynamic Ram
As the necessary and flammable components of the battlefield moving targets, the fuel tank is attacked primarily by the high-velocity penetrator (fragment, projectile, and bullet). Under the impact of the high-velocity penetrator, hydrodynamic ram (HRAM) occurs in the fuel tank, and this event may lead to the fuel spurt. The fuel exiting from the penetration orifice could be highly atomized by the disturbance of aerodynamic, which makes the fuel easily to ignition and fire, thus affecting the survivability of battled field targets. In this paper, the experiment of high-velocity fragments impacting the liquid-filled containers have been conducted to observe and record the process of the liquid spurt. The characteristics of the liquid spurt such as the velocity and the cone angle have been investigated. It has been found that both the impact velocity of the fragment and the shape of the penetration orifice affect the characteristics of the liquid spurt. The expansion and collapse of the cavity are the direct causes of the liquid spurt. Moreover, the relationship between the velocity of the liquid spurt and the pressure in the liquid has been analyzed. The experimental basis for the prediction of fuel spurt distribution caused by high-velocity penetrator impacting the fuel tank could be provided in this study results.
Effects of Structure Characteristics of Projectile on Trajectory and Loads for Oblique Penetration Into Concrete
Three groups of projectiles with different CRH values of ogive-nose, mass center locations, and cone angles of shank are designed to study trajectory and loads of oblique penetration into concrete targets. Impact conditions are taken as striking velocity 600m/s, initial oblique angle 30° and concrete target with compressive strength of 30Mpa. We employed a general differential area force law (DAFL) model of rigid projectile for oblique penetration. An empirical model of free surface effect is proposed for brittle targets. It is shown that structure characteristics have significant effects on trajectories and loads for oblique penetration, i.e. (a) The larger the CRH values, and the closer the mass center locations to the projectile end, the larger the turning angles and lateral deviations of penetration trajectories are. (b)The trajectories of projectiles with ‘cone+ogive-nose’ structures show more stable than those with ‘cylinder+ogive-nose’. (c)All trajectories converge to straight line (linear motion) until stop in the targets, and the trajectories can be divided into turning stage and linear motion stage.
Research on Technology of Launching Projectiles with Preset Attack Angle Using an Artillery
In this paper, the experimental technology of launching a projectile with preset attack angle is studied by using one 152mm ballistic gun. A whole set of technical problems in penetration test of firing preset angle-of-attack projectiles by artillery is solved through reasonably designing the front and rear centering device to preset the attack angle in gun bore, controlling a finite yaw moment by the flight resistance after launch, and determining velocity by net target measurement and attitude by high-speed camera. Test results show that the technology is convenient, with well-controlled attitude of the projectile and satisfying accuracy of preset attack angle, which meets the technical requirements of the penetration test of the preset angle- of -attack projectiles. This test technology has been successfully applied to large-diameter Davis Gun tests of ground-penetrating warheads, demonstrating the whole set of test techniques is feasible and reliable.
Effect of Various Backing Materials on BABT in Ballistic Evaluation of Body Armour
Body armour is being worn by law enforcement agencies and military personnel for protection against ballistic threats. The two key protection parameters for body armour are resistance to complete penetration by a projectile and limited behind armour blunt trauma (BABT), a non-penetrating injury which results when armour is pushed against the body wall during bullet impact. This paper compares the efficacy of various backing materials used in measurement of BABT viz. Roma Plastilina No. 1 (RP#1), a mineral based sculpting clay; Blunt Trauma Torso Rig (BTTR), a biofidelic simulant based test fixture; Ballistic Gelatin, a human muscle tissue simulant. An optimum number of layers of Kevlar woven fabric ballistic material were taken to correlate BABT obtained in various backing materials using 9mm ammunition at different velocities. BABT values obtained in RP#1, BTTR and Ballistic Gelatin were found to be comparable. A correlation factor is suggested for measurement of BABT depending upon the backing material to correlate the test results obtained in various ballistic test laboratories even when different backing materials are employed.
It is widely recognized that angled or yawed projectile impacts on armour can affect the perceived performance due to changes in projectile’s interactions with the armour-. Furthermore, spurious results and greater uncertainty in armour performance can result from variations in yaw angles if not accounted for. While many ballistic test standards limit the allowable incident angle, its measurement has long been accomplished with yaw cards despite having poor precision and possible effect on trajectory. This paper describes the development of a non-contact ballistic yaw sensor for small calibre ammunition and fragment simulating projectiles that meets the requirements of ballistic standards while providing much greater precision and ease of use over that of yaw cards. The use of computer vision methods combined with LED lighting has resulted in a system that is quick and simple to use. The setup, operation, data analysis and accuracy are described with examples of its use.
Accuracy of Empirical Predictions of an Explosives Adiabatic Exponent
The objective of this paper is to determine the best method for calculating an empirical prediction of the Adiabatic Exponent (ï‡), which is reasonably accurate. A literature survey was conducted and many methods found, eight were used and these results compared with trials. From the Gamma Law Equation of State, accurate Adiabatic Exponent and Detonation Velocity enables prediction of the Detonation Pressure. This pressure is difficult and expensive to measure accurately, so simpler methods of determining it are beneficial. A survey of open references concluded that the most complete trials data was by Roth, his complete experimental data is given. These trials measured both the experimental Detonation Velocity and Detonation Pressure. Together with the explosives unreacted density, this gives the Exponent. One method was found to be simple, requiring as input only the unreacted explosive density, estimating ï‡ with a mean error of 0.7% and a standard deviation of 3.6%.
Study on Detonation Loading and Dispersal Properties of Discrete Rod
The detonation loading and dispersal properties of discrete rod are studied. One end planar initiation and centric single point initiation modes are designed to research the wave front output pressure distribution and loading properties of discrete rod, which determine the dispersal and intact properties of discrete rods. The specific impulse distributions of main charge with two initiation modes are calculated theoretically. It shows that the maximum impulse of central initiation is almost 2.18 times that of one end initiation. The velocity distributions of rod’s micro-units are slow-up-and then-fast-down for one end initiation and symmetric for centric point initiation respectively, and the maximum micro-unit velocities of two initiation modes are similar. The effective length of rod for centric point initiation is the 96.3% of original length while for one end initiation is 89.2%. The simulation exhibits the same results with the theoretical analysis. From these analyses, it can be concluded that combined impulse, velocity and effective length, compared with one end initiation, the centric point initiation has better destruction efficiency.
Simulation Study on EFP with Stable Tail Fins Formed by Polygonal Shaped Charge Liner
To ensure the flight stability of a modern explosively formed projectile (EFP) with a high standoff distance, the feasibility of forming an EFP with a high length-to-diameter ratio (L/D) by a polygonal charge liner was investigated by using a three-dimensional simulation. The results revealed that an optimal EFP structure with a large L/D and stable tail fins could be achieved when using 0.8De (diameter of liner circumcircle) as the outer curvature of the thickness-varying hexagonal hemispherical liner, 0.0325De as the top thickness, and 0.2 as the bottom-to-top thickness ratio. However, when the number of edges was more than 12, the tail fins would start to transition to pleated fins and become more prone to fracturing.
Effect of Detonation Wave Profile on Formation of Explosively Formed Projectile (EFP)
Explosively Formed Projectiles (EFPs) are used in numerous modern top attack artillery ammunition systems because of their advantages such as higher effective standoff distance and better behind armour effects (BAE) after target penetration. In an EFP warhead, a hemispherical liner under precise initiation and explosive action gets deformed to a compact and aerodynamic shape of projectile, which has high penetration potential due to high EFP velocity is in the range of 1.5-2.5km/s. In this paper, the effects of detonation initiation methods on the formation of EFPs are studied using an EFP warhead of dia.195mm. Two potential materials OFE copper (Ï=8.93gm/cc) and tantalum (Ï=16.6gm/cc) are used as liner materials for EFP warhead. EFP’s velocity, shape and size are studied using AUTODYN Numerical Nonlinear 3D hydrocode software. An Eulerian-Lagrangian approach has been used with Eulerian description of the explosive and casing parts whereas a Lagrangian description is used for the liner part. The liner material and casing material were modeled with a shock equation of state. The Explosive is modeled with JWL equation of state. Two different initiation detonation methods are chosen for numerical simulation. In single point initiated detonation method, warhead is initiated from the centre of the warhead from the rear end and it has been observed that EFPs velocities are 1.5km/s and 0.97km/s in OFE copper and tantalum liners respectively. In case of peripheral initiated detonation method, which favours better perforation performance because of planar shock wave striking normal to the liner material, EFPs velocities are 1.9km/s and 1.1km/s in OFE copper and tantalum liner material respectively. It was also observed that EFP length is more in case of OFE copper liner material whereas EFP diameter is more in tantalum liner material. Length to diameter (L/D) ratio of EFPs was found to be greater in case of peripheral initiated detonation
Study on the Influence of Wave-Shaper on the Damage Elements Formation of PELE/EFP Mode Conversion Warhead
Mode conversion warhead is one of the key points in the field of warhead research. In this paper, based on the understanding of the current research situation of the mode conversion warhead, the influence of the wave-shaper on the damaged elements formation of PELE/EFP mode conversion warhead was studied by combining theoretical analysis with numerical simulation. The results show that the warhead structure in this paper can form two kinds of damage elements: PELE and EFP; In EFP mode, the larger diameter of the wave-shaper, the larger the length of the damage element, the length-to-diameter ratio, the head-to-tail speed and the head-to-tail speed gradient; The length of the damage element varies from 105.58mm to 126.57mm, and the length-to-diameter ratio varies is 3.36~3.94; In the PELE mode, the change in the diameter of the wave-shaper has less effect on the formation of the damage element.
Test to Determine the Response Level of Heterogeneous Explosive by Fragment Shock Initiation
The study of the criteria for the impact initiation of heterogeneous explosives is of great value in the field of power design and for the safe application of explosives. This paper proposes two methods for assessing the response level of a heterogeneous explosive subjected to fragment shock initiation. Experimental studies have shown that for flake explosives (difficult to process the circumferential casing), that is, the charging form of the cover interlayer, the degree of explosive reaction can be assessed by the flying speed of the cover plate. For thick explosive that can process the circumferential casing, a test method was carried out to assess the reaction degree of the explosive by considering the average area of the aluminum plate’s perforation.
Numerical Study on the Axial Initial Velocity Distribution Characteristics of Preformed Fragment
Initial velocity of fragments is one of the key parameters to evaluate the lethal performance of high explosive projectile. Based on the modification of Gurney equation, axial initial velocity distribution characteristics of preformed fragments warhead under three different detonation modes, including center detonation, single-ended detonation and double-ended detonation, were studied by numerical simulation and least square nonlinear fitting method. The calculating formulas for axial initial velocity of fragments were fitted. Furthermore, the fitting formulas were verified by changing the mass of explosive and the shape of fragments. Finally, the computation accuracy of the fitting formulas and the existing formulas were compared. Simulation and comparison results showed that initial velocity of fragments calculated by the fitting formulas was closer to the simulation results than that of the existing formulas and the error of the fitting formulas were below 10%. It clearly demonstrated that the fitting formulas are suitable for predicting the initial velocity of preformed fragments.
Dynamic Response Analysis of Warhead Under Dropping
A simulant warhead is proposed in this paper to analyze the dynamic responses under dropping, the work circs of dropping is 32 meters, which is imitating unexpected dropping after launching but delayed ignition or absence of ignition. Dynamic responses of warhead and interior electronic method by using three-dimensional finite element software is analyzed. A typical warhead has been chosen as a test-thing, the key data about distortion, stress distribution and acceleration are all attained, which support the security design for warhead and interior electronic method.
Thin Flyer Impact Initiation Threshold Comparison of HNS-IV, CL-20, CL-20/HMX Co-Crystal in Slapper Detonator
Slapper detonator consists of exploding metal foil, thin polyimide flyer, spacer (barrel) and high density explosive pellet. When high electrical energy applied in short duration, the metal foil explodes, to accelerate thin polyimide flyer to a velocity of 2-3 km/s. The impact of flyer on explosive pellet leads to prompt initiation by shock-to-detonation phenomenon. HNS-IV explosive is widely used in this application as it is highly insensitive and thermally stable with small critical diameter. However, the HNS-IV explosive has limitations of batch-to-batch variation, low velocity of detonation (VoD) (~7200 m/s) and low CJ pressure (20 GPa). Recently, CL-20 explosive has emerged as one of the potential high energy material for application in slapper detonator. CL-20 has high VoD (~9400 m/s) and CJ pressure (~48.2 GPa) and can be used in miniaturization of futuristic explosive devices. In this research work, HNS-IV, CL-20 and CL-20/HMX co-crystals were processed using novel technique of nozzle based solvent-antisolvent method. The processed explosives were characterized for particle size, shape and morphology. Experimental prototypes of slapper detonators were fabricated with same configuration of flyer, barrel diameter and exploding foil dimensions to evaluate and compare the performance. The threshold trials were carried out using Bruceton test. Comparative results of explosive characterization and threshold initiation voltage of the three explosives is presented. The particle size of all the three explosives is in the range of 0.5 to 9 μm and the threshold initiation voltages for HNSIV, CL-20 and CL-20/HMX co-crystals are in the range of 1.75 kV, 0.9 kV and 1.5 kV respectively with standard deviation of ±0.1 kV. It is observed that CL-20 has lowest threshold initiation voltage; however, it is more impact and friction sensitive. The sensitivity properties of CL-20 can be tailored by making co-crystals with HMX. This enables to get insensitive and more powerful slapper initiators with advantage of miniaturization, as CL- 20/HMX co-crystal has sensitivity and thermal properties near to HMX and better than CL- 20.
Underwater Demolition of Steel Rods by Contact Explosions
This research is dedicated to the effect of underwater contact explosions on steel rods. The work is inspired by problems the Dutch Army Engineers experienced with the effective demolition of steel structures under water. Selected parameters which could affect incomplete demolition were investigated experimentally. These parameters included the amount of explosive, the contact geometry and the thickness of the spacer between explosive and steel. For the experiments a plastic explosive and cylindrical steel bars of 100 cm length and 5 cm diameter were used. A main cause of failing demolition can be attributed to insufficiently following the guidelines. The explosive charge should be in close contact with the target material. Furthermore, the optimal geometric arrangement of the plastic explosives was found to be a 120 degrees covering around the steel bars. The latter strategy achieved a demolition of the rods at half the amount of explosive as prescribed.
Deformation, Fragmentation and Acceleration of a Controlled Fragmentation Charge Casing
This paper presents a study on the ability of two finite element software to predict the deformation, fragmentation and acceleration of a controlled fragmentation charge casing. In order to acquire data for the evaluation, a series of instrumented experiments have been performed using a laboratory charge with an internal grooved casing. Comparisons to experiments show that both software can predict the change in deformation behaviour when the groove depth increases, from tangential necking for shallow grooves to radial punching for deep groves. Both software could also reasonable well predict the acceleration of the fragments, though both overestimates the terminal velocity for the charge with the deepest grooves. This is an extended abstract of a full paper published in Defence Technology, 2019.
Research on the EFP/PELE Multi-Mode Conversion Warhead Technology Based on the VESF Initiation System
The EFP/PELE multi-mode kill element is obtained by adjusting the detonation waveform. Considering the instability of the installation process when the partition is used as the waveform adjuster, a new type of the EFP/PELE multi-mode Warhead based on the VESF initiation system is designed in this paper. The influence of liner materials on the damage effect were compared and analyzed. The results show that the larger the elastic modulus of the outer liner material is, the more favorable it is for the PELE forming, which is not conducive to the EFP forming. The large difference in acoustic impedance between the liner materials will lead to overstretch of the inner liner. The inner liner material with small elastic modulus and large Poisson's ratio is suitable for the lateral effect of projectile. Considering comprehensively, the multi-mode kill element has the best performance when the liner is composed of Iron-Teflon.
Effect of HE Grain Size on Shaped Charge Jets
The effects of the detonation front roughness on the liner of a shaped charge was investigated in an experimental program. Three batches of the PBX KS32 (HMX/HTPB 85/15) with different distributions of the HMX grain size were manufactured and tested in an experimental program. A first test series regarded the roughness of the indentations on copper plates caused by the detonation front. In a second series, specially designed shaped charges filled with the different HE batches were fired in front of FXR and were evaluated with regard to tip velocity, jet breakup, jet length and particle drift. The tests revealed a distinct influence of the HE grain size on the jet quality and especially on jet breakup and cumulative length.
Effect of Phase Distribution on Reaction Behaviors of PTFE/AL Reactive Materials
The polytetrafluoroethylene/aluminum (PTFE/Al) reactive material is one of the new energetic structural material containing good structural strength and high energy density. However, limited by traditional preparation methods, it is difficult to get uniform microstructure, while the presence of agglomeration which decreased the contact area between oxidizer and fuel would limit the reaction efficiency. In the paper, we prepared two kinds of Al particles with different particle size, and demonstrated two fabricated methods to adjust the distribution of phase, thus achieving the goal to control the reaction rate and extent of reaction. Thermal characteristics, reaction heat, specific volume of explosive, and reaction processes under high speed impact were measured to evaluate the effect of phase distribution on reactive characteristics of PTFE/Al reactive material. In comparison with the material fabricated from traditional method, the material containing uniform distribution of phase exhibited a higher reaction efficiency, bigger explosive specific volume, and longer duration of the reaction under impact.
Fragmentation from Detonations and Less Violent Munition Responses
An increasing number of munitions now show less violent responses than detonation in cook off or impact scenarios. The detonation of a warhead typically leads to well reproducible fragmentation effects. Deflagrations and explosions may still rupture the munition casing, but fragmentation is typically limited to just a few large fragments with a relatively low velocity. Fragmentation modeling has evolved significantly with increasingly realistic predictions, even for less violent explosions and deflagrations. Although deflagrating warheads produce only a few fragments, these fragments may reach large distances. Estimates of deflagrating warhead fragment trajectories can be done using platelike fragments. Conventional safety distances are not well suited for this situation. For illustration purposes a simple model of Individual and Group Risk was applied to a case study comparing detonating and deflagrating warheads.
Effect of Geometric Out of Planar Gap on Jet Formation in Multi-Pallet Type Charge Mass of Shaped Charge Warheads
Shaped charge studies are being carried out from decades. The shaped charge penetrators are the high velocity jets formed from liners when collapsed axially. In order to further increase the velocity, the waver shaper is used which change the shape shockwave and increase the rate of collapse. So, to assemble this wave shaper and liner in the charge mass different methods are used such as in-citu pressed/ casted. But when they are assembled with two different billets it is difficult to ensure the perpendicular, surface to surface contact etc. due to tolerances provided for hardware manufacturing or any other machining error. Due to above mentioned problems there may be angular or planer gap between two billets, offset initiation etc. The effect of these parameters on jet is presented this paper using ANSYS AUTODYN simulation software
Simulation Study on Low-Density Jets Formability and Damage Characteristics of Different Charge Structures
ERA (explosive reaction armor) makes the traditional anti-tank weapon face unprecedented challenge. To defeat an ERA, a tandem shaped charge is the most used ammunition. Whether the front warhead of tandem warhead can detonate the reactive armor reliably determines whether the rear warhead can achieve high efficiency damage to the armored target. The existing shaped charge front warhead mostly adopts a metal shaped jet, which can effectively initiate the ERA, but disturb the rear main shaped jet. In order to avoid this shortcoming, reduce the mass of the front warhead and improve the penetration power of the rear warhead, the low-density material Plexiglas is used as liner material in this paper. By comparing the formation and damage characteristics of low-density jet with different charge structures, it is expected that ERA and after-effect can be destroyed efficiently. The results show that the shaped charge structure with wave-shaper is better than the shaped charge structure without wave-shaper regardless of jet formation performance or the penetration ability of the ERA and after-effect target. The low-density jet formed by the shaped charge structure with wave-shaper can reliably detonate the ERA, and the mass of the shaped charge structure with wave-shaper is smaller, so it can reduce the mass of the front warhead, in turn, the penetration power of the rear warhead in tandem warhead is improved. It provides a reference for improving the damage ability of tandem shaped charge to ERA.
Defeating UAVs Through Novel HPEM Effectors
Unmanned aerial vehicles (UAVs) are sophisticated, autonomous, low-cost systems that may become a threat when supplemented with energetic charges or improvised explosive devices (IED) as deadly payloads. While single UAVs may be defeated through air defense systems or new laser effectors, a swarm of them may, however, saturate such systems, especially when they fly coordinated attack patterns. Another encouraging concept generates either omni-directional, near-distance or directed, far-distance electromagnetic effects consisting of an explosively driven flux compression generator (FCG), an electrical opening switch, and the subsequent shaping of the electrical pulse into a high frequency (HF) radio signal transmitted by an antenna. This enables a promising compact design approach for integration into mobile effectors such as missiles or shoulder-launched munitions defeating swarms of UAVs as well as other electronic systems, devices, and components. FCG prototypes, a test setup and diagnostics including a Rogowski probe for current measurements were developed for proof-of-principle trials with iutput currents measured of several hundreds of kA. This complies to a current amplification factor of approx. 30 also predicted through a system simulation. In other subcomponent tests, a continuous and a pulsed microwave generator were used for generating radio signals transmitted by a horn antenna. The effectiveness of the emitted signal is eventually evaluated against commercially available UAVs like a Phantom 4. These vulnerability tests were performed at an anechoic chamber with parameters varied including antenna distance and direction to the target as well as pulse and idle times of the interference signal. These experimental results were also used for verifying simulation models created with LTspice.
Shock Wave Propagation and Coupling Characteristics of Dual-Source Underwater Explosion
Shock wave propagation processes of dual-source underwater explosion are researched. Basing on dimensional theory, the variation of peak pressure and specific impulse gain coefficient with dimensionless explosion distance and dimensionless spacing are analyzed. The results show that there are high-pressure coupling and low-pressure coupling regions in the shock wave field. The shock wave peak pressure and specific impulse are functions of dimensionless explosion distance, dimensionless spacing and azimuth. When the azimuth is 90ï‚°, conclusions are as follows: when the dimensionless explosion distance is greater than 30 and the dimensionless spacing is greater than 2.48, the gain coefficient of shock wave peak pressure is stable at 30%~50%, when the dimensionless explosion distance is constant and less than 30, the gain coefficient of shock wave peak pressure is maximum in the dimensionless distance range of 9~13, and the specific impulse gain coefficient increases with the dimensionless distance in the range of 4.96~24.81.
Numerical Study of Air Frame Behaviour on Fragmentation Pattern in Multi Layered Pre-Formed Fragment Type Warhead of Modern Rockets
The artillery rocket system is the sophisticated type of defence system. One of it is Preformed fragment type warhead. The tungsten fragments-ball, needles, cubes etc. are arranged around the charge mass in such a way that on initiation the fragments are propelled with very high velocity by rupturing the ballistic casing. These ballistic casing can be made of different materials according to the aerodynamic loading, structural loads etc. Generally used casing materials are FRP, steel, aluminium. Due to difference in the material properties the fragment velocity, energies and the pressure generated are affected. To study these effect static and dynamic trails prove costly and time consuming. So an alternative method of simulation of warhead with different ballistic casing is presented. During simulation the multilayer fragments are replaced by single layer having equivalent mass as it is difficult to model 20000 no of fragments. Hence the results obtained are in good agreement with the available data.
The Effect of Current Waveform on Shaped Liner Driven by Electromagnetic Energy
The US Air Force Research Laboratory (AFRL) has proved that shaped charge liner can be driven by strong electromagnetic energy to form jets. In this work, we establish a theoretical model for jet formation driven by strong electromagnetic energy. MATLAB software was used to calculate a liner in the experiment of reference 7 driven by electromagnetic energy under different current waves through analytic formula. Collapse velocity and jet velocity under different current waveforms were obtained. The results showed that the current waveform has a great influence on jet forming. The tip collapse velocity and jet velocity is positively correlated with peak current and the tail collapse velocity and jet velocity is positively correlated with rise time.
Influence of Structural Characteristics on EFP Formation Under Different Liner Materials
To further research the relationship between structural characteristics and materials of liner on explosively formed penetrator (EFP) formation, by using the LS-DYNA finite element software, the coupling effects of the structure and material on the formation of EFP were simulated, considering six structures (truncated, conical, tulip, arc, horn, arc cone liner) and five materials (aluminum, OFHC copper, Armco iron, tantalum, tungsten alloy). Under the condition of similar liner structure and mass, liner structure has little effect on the velocity of EFP, however, density play a remarkable negative relevant role. In the respect of EFP formation, OFHC copper liner with good elongation will obviously stretch to reach a lager length-diameter ratio (L/D) at all presented structures in this article. Furthermore, liner structure should be identified to a specific material and objective requirements. Although formed EFP with low solidity, arc liner makes Armco iron, tantalum and tungsten alloy to develop L/D and flight stability. Truncated liner has great benefit to OFHC copper EFP on L/D and solidity at the expense of little flight stability. Aluminum EFP of arc cone liner has both lager L/D and suitable solidity and flight stability.
The Influence of Eccentric Wave-Shaper on Shaped Charge Jet Performance
For a SCJ (shaped charge jet), the wave-shaper deviation caused by defects in assembling tolerance affects the propagation of detonation wave and the liner collapsing. In this paper, Shock Physics Explicit Euler Dynamic (SPEED) software was applied to simulate the jet forming and penetration process with built-in offset wave-shaper. The detonation wave and the compression process were observed. Morphology of the deflected jet and the asymmetric entrance profile of the jet penetrating target were obtained. The calculation results show that the wave-shaper off-axis will make the detonation wave asymmetrical and the lateral velocity of the jet increases as the offset increases which causes lateral effects and makes the hole entrance irregular. When the wave-shaper offset reaches 0.0244CD, the penetration depth of the deflected jet decreases more than 50% compared to the stable jet.
Effect of Fragmenting Buried High Explosive Projectile (152MM HE FRAG OF-540) on Military Ground Vehicles
Simulation of Military ground vehicles subjected to buried landmines, and Improvised Explosive Devices (IED) has been carried out by many researchers, and military establishments to understand the effects in detail. But the ability to predict the effects of fragmenting IED’s on military ground vehicles is little known in simulation community. Hydrocode simulation such as Eulerian simulation and Arbitrary Lagrange in Eulerian (ALE) simulation coupled to vehicle structure is widely used methodology to characterize buried detonating IED. But for fragmenting IED’s capturing the fragmentation and fragmenting elements are necessary and ALE may not be able to capture it. There are several statistical and empirical formulations that are available to approximately estimate the number of fragments, but does not provide sufficient information about the velocities of the fragments. In this proposed study, a 152mm High Explosive (HE) OF-540 fragmenting projectile was modelled in detail per geometry and buried 100 mm deep inside the soil. This fragmenting projectile was coupled to U.S. Army’s Ground Vehicle System Center (GVSC) developed generic hull (GH) structure to understand the impact effects of fragmenting fragments. Three different analysis were carried out Projectile buried in soil with adaptive SPH projectile casing, Projectile buried in soil coupled to GH structure with projectile casing as ALE and projectile casing as adaptive SPH methods. Results from all the three analysis were thoroughly analyzed and findings from these analysis is presented in this paper. Solid element formulation is well suited for shock waves, crack propagation and fragmentation problems was used in modeling all the structural and projectile components using commercially available structural code LS-DYNA-3D.
Numerical Simulation Analysis of Glass Fracture Under Blast Loads
The main methods in LS-DYNA software for the simulation of dynamic fracture behavior of glass under blast loads were introduced and reviewed. Bond-based peridynamics computational model (PD model) has significant advantages over other methods for the brittle fracture analysis, especially for three-dimensional problems. Different mesh sizes and TNT charges were investigated on the glass fracture under blast loads by PD model. Simulation results show that annular damage arises in the border of glass panel at first, then it propagates to the center quickly. After some time, radial cracks emerge in the center of the glass panel. The center glass separates forwards from the panel, while the surrounding glass splashes reversely. The more explosive mass, the less size of glass fragments.
Liner Collapse Related Issues in the Design of Low L/D Shaped Charges
Low length to diameter (L/D) ratio shaped charge, having L/D ratio in order of 1.0-1.1, can be designed to achieve comparable penetration performance to conventional shaped charges having L/D ratio in order of 1.3 to 1.6. The design includes suitable combination of liner configuration and waveshaper geometry to get desired penetration. Due to dimensional restrictions, waveshaper is positioned very close to liner causing sensitive variation of liner collapse angle, jet velocity and velocity gradient. Selection of liner and waveshaper location results in effective shaped charge even with reduced dimensions and explosive weight. A design of 115 mm diameter shaped charge has been discussed to highlight issues related with design of low L/D shaped charge warheads. One dimensional PER theory along with two-dimensional hydrocode simulation tools were used for analysis.
Experimental Study on Design of Linear Cutting Charge and Cutting Steel Structure Parts
Aiming at the demand of a variety of metal structure target cutting, a linear cutting charge test device is designed in this paper. The formation process of the jet of the Linear cutting charge model is simulated. As can be seen from computational results, the linear cutting charge with the liner of copper material and cylindrical shape is used to form a cutting knife-type jet with a front-end speed of 4.2 km/s~4.3 km/s. The cutting tests for railway rails and steel plate were carried out. It can be seen that the linear cutting charge designed in this paper has achieved a good cutting effect.
Effect of Wave Shaper on Optimum Standoff of Copper Liner Shaped Charge Against Steel Target
A wave shaper is embedded in charge can increase the jet tip velocity and the penetration performance, but thus affects the optimum standoff of copper jet. To investigate the influence of wave shaper on optimum standoff, numerical simulations based on LSDYNA code with the three-dimensional axisymmetric model are conducted, including the propagation behavior of detonation wave, the jet velocity and its characteristics, and penetration depth of copper jet, and the experimental verifications are used. The simulations show that the spherical detonation is converted into the conical detonation wave by using the wave shaper, decreasing the incident angle of the detonation wave at the top of the liner, which will increase the jet tip velocity and jet length but decrease the jet tip diameter. The penetration depths and hole-diameters of experimental are well agreement with the simulations. Under the same standoffs, the penetration depths of copper liner shaper charge with wave shaper are higher than that without wave shaper, whereas the hole diameters with wave shaper are lower than that without wave shaper. When the cone angle of copper liner is 60°, the optimum standoff of copper jet with wave shaper is about 1.5 CD~2.5CD, and the without wave shaper is about 2.5 CD~3.5CD.
Bore-Center Annular Shaped Charges with Different Liner Materials Penetrating into Steel Targets
Abstract：The bore-center annular shaped charge (BCASC) is a new type of shaped charge which can generate a larger-diameter hole in steel targets than classical shaped charges. In this paper, the influence of three liner materials, i.e. molybdenum, nickel and copper, on BCASC formation and penetrating into steel targets was investigated by experiment and numerical simulation. The simulation results were well consistent with the experimental results. This study showed that, at 0.50D standoff distance, the axial velocity of the molybdenum projectile was lower than that of the nickel and copper projectiles. The nickel and copper projectiles had almost the same head velocity. The absolute values of the radial velocity of the molybdenum projectile head was lower than that of the nickel and copper projectiles. However, at 0.75D standoff distance, the absolute values of the radial velocity of the molybdenum projectile head became much greater than that of the nickel and copper projectile heads. The projectile formed by BCASC with the molybdenum liner had the highest penetration depth of 61.5 mm, which was 10.0% and 21.3% higher than that generated by the copper and nickel projectiles. This is an extended abstract of a paper that will appear in Defence Technology in 2019.
An Experimental Study of DDT Tubes with Different End Restraint Materials
The effects of the strength of the tube end restraint material on the deflagration to detonation transition (DDT) of an explosive, were assessed, using coaxial ionization probes. An 8701 charge was employed as a model explosive, together with #45 steel, aluminum and nylon tube end caps. The appearance of a DDT was determined based on the indentation of a steel witness plate as well as the recovery of tube fragments and the extent of perforation of a wooden target. The experimental results show that the detonation wave velocity determined by the ionization probe method remained constant when varying the end restraint materials, and that the inducing detonation distances associated with using steel, aluminum and nylon as end caps were 4.2, 5.2 and 6.2 times the charge diameter. Thus stronger end restraints, increased the degree of reaction of the explosive as well as the tendency to undergo a DDT.
Experimental Study on Dynamic Response of Reactive Structure Material Under Detonation
When the reactive structure materials (RSMs) are used as projectile to damage the target, the advance activation of RSMs under explosive launch will seriously affect its effective damage ability. In order to test the characteristics of RSM, an innovative explosive driving device was designed and adopted to drive two typical RSM samples impacting a 6-mm thick medium carbon steel target at approximately 2200m/s. The vacuum powder metallurgy sintered tungsten-zirconium material projectile with a diameter of 9.0mm and density of 10.01g/cm3 named sample A. Sample B was vacuum plated with 0.1-mm thick ductile alloy based on sample A. The fragmentation and activation behavior of two samples under explosive loading were observed by high-speed camera (PHOTRON, FASTCAM APX RS). The damage patterns of target were obtained to compare the difference of the two samples’ comprehensive damage capability. Moreover, the two samples’ dynamic behavior have been analyzed based on the experimental data, which proved that the coating structure played an important role in keeping integrity of RSM under explosive loading. The results of the current work provide experimental method and innovative RSM structure for further studying the dynamic behavior of RSM under explosive loading.
Effect of Confinement on the Performance of Fuel Rich Explosive Charges
Fuel rich explosive charges consisting of excess metal in the formulations are designed to create enhanced blast effects through the post detonation reactions in anaerobic and aerobic phases. For metallised explosives, the nature of confinement can significantly affect the casing rupture time and the expansion of detonation products. The confinement is likely to increase the residence time of heated metal particles in the detonation product zone thereby improving the ignition and combustion efficiency. In the present study, the effect of casing on the performance of a fuel rich explosive composition based on RDX, Al and HTPB was studied in field experiments. The results are correlated to the observations from numerical modeling of the detonation, case rupture and blast phenomena modeled using thermochemical equilibrium code and eulerian hydrocode SPEED. The results suggest that the confinement helps in enhancing the blast and thermal impulses which are the primary performance parameters for this class of explosives.
Evaluation of the Dynamic Fracture Characteristics (Plasticity) of Shaped Charge Jets at Different Strain Rates and Characterized Initial Liner Microstructure
The breakup phenomenon in shaped charge jets have been studied for numerous designs over many decades. The main focus of this research was to demonstrate the influence of varying strain, strain rate behaviour on shaped charge jet break up times with copper liners which have fixed grain sizes/microstructures. The overall strain and strain rate was varied by changing shaped charge liner angle and by using different initiation systems. Two liner designs 60â° and 120â° (full angle, respectively) were evaluated with comparable microstructures. The strain and strain rate of shaped charge jets was further modified with two initiation systems (point initiation and peripheral initiation). ANSYS AutodynTM simulation software was used to model the various shaped charge designs to allow a strain, strain rate variance by varying the jet tip and tail velocities. Double flash x-ray analysis was conducted on all shaped charge warhead designs and then analysed with image detection software to obtain the jet parameters to a high degree of accuracy. The cumulative length, breakup times, velocity difference, tip and tail velocities were calculated for each design. These parameters were used to evaluate a “dynamic fracture parameterâ€ (or plasticity indicator) for the various designs. It was found that this parameter was constant for all the designs if it is evaluated from jet tip to a particular jet velocity.
Investigation on the Influence of the Initial RDX Crystal Size on the Performance of Shaped Charge Warheads
Copper lined waveshaped shaped charges of particular design and liner metallurgy were used to investigate the effect of explosive crystal size on the resultant shaped charge jet parameters. Composition A3 with RDX of three different average crystal sizes, i.e. 30μm, 100μm and 300μm were used in the investigation. All other parameters in the charge were kept constant and in particular, care was given to obtain consistent dimensional quality and liner microstructure, in order to prohibit the variation of other parameters. Specific flash-X-ray diagnostics were used in field tests to obtain the jet parameters from multiple firings of similar charges. It is found that the varying crystal size of the RDX has a marginal influence in the total jet length of the jets. However, it is also found that there is less variation between firings in the jet parameters for jets from the charges loaded with the crystal size of 100μm.
Study on Jet Formation and Penetration of Square Cross-Section Shaped Charge
The square cross-section aviation weapon platforms have lower radar cross-section and favorable aerodynamic characteristics that make it desirable. It is necessary to study the jet formation and penetration of square cross-section shaped charge (SSC). A theoretical analysis on collapse velocity of the liner of an SSC is performed. Numerical simulations are carried out by LS-DYNA to compare the distinctions of jet formation and penetration between an SSC and a circular cross-section shaped charge (CSC), where the diameter of CSC is equal to the length of the side of SSC. The result shows that the collapse velocity of SSC is periodic. The velocity of the jet top of SSC is slightly higher than that of CSC. The jet of SSC is almost the same length as the jet of CSC at different moments. The penetration of SSC is deeper than that of CSC at stand-off =80,120,160mm.
Experimental Studies of Explosion Energy Output with Different Igniter Mass
For study the energy output law of cylindrical charge with shell induced by different input energies, four different black powder masses were selected to ignite the main charge. Fragmentation degree of the shell was qualitatively analyzed by the area of holes on the witness plate and the recovered fragment mass. Through theoretical analysis, established the functional relationship between the average mass of fragments and the relative energy output of warhead, obtained how the relative energy output of charge changed with different initial energy input. The results showed that the change of input energy could lead to obvious variation in fragment characteristics, and could also control the output of charge. When the igniter mass increases from 1.55g to 5.00g, the relative energy output of the charge increases by 26.28%. Excessive initial input energy will destroy the shell confine in advance, resulting in a decrease in the relative energy output of charge.
Study on the Characteristics of Non-Cohesive Jet Formed by Two-Phase Alloy Liner
It is hard for general shaped charge jet to enlarge a large crater hole, when it penetrate the concrete target. The non-cohesion jet may do it. In this paper, the character of the noncohesion jet formed by shaped charges which liner were two phase alloy (titanium alloy) were studied by X-ray experiment and the penetration ability was firmed through DOP experiments. The results show that compare with OFHC jet, the non-cohesion formed by the TC21 liner and NiTi liner can enlarge the crater hole and have certain penetration ability.
A shaped charge is an explosive device used to penetrate thick targets using a high velocity jet. A typical shaped charge contains explosive material behind a hollow cavity. The hollow cavity can be lined by a matching metallic shape the purpose of which is to focus the energy of expanding gaseous products released during the detonation of high explosive thereby propelling the liner elements hydrodynamically forming a coherent elongated jet of liner material. In this study shaped charge jet parameters are calculated using indigenously developed one dimensional code and using copper liner of conical geometry. Although many codes are available in literature to study this phenomenon, this code has distinctive features to model the motion of liner elements due to explosive loading, jet formation, elemental strain and strain rate developed on each liner element, jet breakup time and target penetration through application of a series of analytical approximations. The shaped charge liner was treated as a series of liner points. The code used Gurney formulation assuming polytropic expansion of gaseous detonation products to predict the velocity of each liner point. The collapse angle of the liner was calculated using a modified Taylor Angle formulation. The shaped charge jet parameters were calculated using the Pugh-Eichelberger-Rostoker jet/slug formulation theory. Non-steady state hydrodynamic theory of jet formation was used to develop the code[2]. The structure of the code is intended to provide flexibility in shaped charge design and modeling techniques. It has the capability of being customized from the user’s/designer/explosive processing perspective, warhead fabrication point, so that improvisation can be done at development stage itself. To ease the calculations and save the time the code was written in C language. Developed code was validated for various jet parameters with experimental data available in literature[5], [11], [14] and the results were within the range of +10%.
Exploration of a Design Concept for Cylindrical Shaped Charges
For essentially all the long history of shaped-charge development, the utility of a shaped charge has been measured by its depth of penetration. This metric stems both from the historic targets of interest and the traditional output characteristic of a conical shaped charge, which produces a stretching jet with penetration depth proportional to jet length. The stretching jet eventually particulates which limits the effective standoff distance of the charge. A cylindrical liner configuration to produce a steady-state, coherent, non-stretching jet is analyzed and discussed here. Advantages from a cylindrical configuration are that (1) jet speed is twice the effective detonation speed, (2) penetration is relatively insensitive to standoff, and (3) jet length and diameter are independent design parameters. Jet length is a function of charge length and can be increased with a linear increase in both charge length and mass. Simulation of a jetting 60 mm diameter copper liner suggests a stable jet is achievable.
Exploding Bridge-Wire Initiation Performance of UltrafineCL-20 Explosive
CL-20 is the most powerful energetic material presently available having highest crystal density and the highest detonation velocity among usable nitramine explosives. It is one of the most promising energetic materials for future military applications for miniaturization of explosive devices and initiation systems. Though chemical and physical properties of CL-20 are well reported, literature related to its shock initiation behavior is limited. In this research work, ultrafine (uf) CL-20 was prepared and characterized. Thereafter, Shock initiation behavior of ufCL-20 was studied by exploding bridge-wire phenomenon using it as initial pressing charge. The performance was evaluated in terms of all-fire energy and was compared with most commonly used explosives in EBW devices viz PETN and RDX.
Study on Shaped Charge Jet Impact and Penetration into High and Ultra-High Strength Reactive Powder Concrete Targets
Reactive powder concrete (RPC), a composite that is cured to have ultra-high compressive strength, high durability and high toughness, has been developed in recent years. In this study, the penetration model as shaped charge jet (SCJ) into RPC targets was investigated. The penetration resistance and the anti-impact performance of RPC targets were analyzed. Restlts showed that depth of penetration (DOP) experiments had a good agreement with the calculations. The DOPs of RPC targets created by shaped charge jets are more sensitive to the compressive strength than cavity diameters. In addition, the effect of the jet velocity on penetration resistance was significantly greater than concrete strength do. The higher the jet velocity was, the smaller the compressive strength affected the penetration resistance. With the increase of the RPC compressive strength, the increase of the penetration resistance showed a gradual downtrend. The incrementary ratio of the penetration resistance with the increasing RPC compressive strength was smaller when the jet velocity range was 5.0~10.0km/s compared with that when 1.0~5.0km/s. Moreover, the impact crater depth is affected more by compressive strength of concrete than that by steel fiber volume fraction. The area of the impact crater is no longer reduced as the volume fraction of steel fiber is more than 2% (compressive strength is more than 180MPa), while the depth and volume of impact crater are still decreasing.
A Method for Measuring the Jet Tip Velocity
In order to obtain the jet forming morphology and jet tip velocity, using the SIMD16 ultrahigh speed camera to capture the shaped charge jet process. The jet shape profile at different times of the shaped jet forming stage is obtained. The jet tip velocity is measured and compared to the calculated value. The results show that the forming process of shaped jet by the ultra-high speed camera. By optimizing the parameters such as exposure time, it is possible to obtain clear photos of the jets at different moments and calculate the jet tip velocity according to the jet’s motion path. The calculation result is basically consistent with the theoretical calculation values. The ultra-high speed camera incorporates a beam splitter and enhancer to minimize the exposure time of camera to 3ns. It can be used to capture and study transient phenomena such as the shaped charge jet forming process, providing research on the design and damage mechanism of shaped charge.
Interface Study of Explosive Welded AL-Steel Joint Using Ultrasonic Phased Array Technique
Explosive welding is advantageous for joining dissimilar materials having large surface area with excellent metallurgical bonding. However after explosive welding, the major area which one needs to focus is the bonded and de-boned area inspection and evaluation. In this research work, pure aluminium (Al) plate is explosively welded with Mild Steel (MS) using explosive of low Velocity of Detonation (VoD) . The welded plates are then verified and examined through non-destructive testing technique named Phased Array based Ultrasonic Testing (PAUT) to check bonded and de-boned areas in welded plates. Optical microscope and Vicker’s micro-hardness tester was also studied for Al-MS joints. Successful bonding of bimetallic plates was observed and ultrasonic testing results also confirmed that maximum area was successfully bonded and only some area towards the end of detonation was left de-boned. Obtained results clearly reveal, explosive welding technique using explosive of low velocity of detonation, as a promising technique to join bi-metallic components, which has wide applications in industrial and defence sectors.
Simulation Analysis of the Influence of Fuel Tank Fuel on the Distribution of Power Field in Missile Warhead
This paper studies the influence of fuel tank and fuel on the distribution density and fragmentation velocity of the fragment in the missile fuel tank by LS-DYNA numerical simulation and analysis. The analysis of simulation results show that the peak value of fragment number in full oil state changes from near the upper and lower sides in no oil state to near the horizontal direction, the peak number of fragments can be increased by about 9%, and the velocity difference of fragments between the no oil and full oil condition increases with the increase of the oil layer thickness, the maximum velocity difference of fragments is 451.8 m/s. The eccentric placement of warhead and thickness of fuel tanks also affects the velocity of fragments. The simulation results are basically consistent with the experimental results. It provides a theoretical reference for the design and power evaluation of the fuel tank fragment warhead.
Research on the Application of Insensitive Explosives in High Explosive Warhead
In order to enhance the insensitivity of ammunition, the numerical simulation and experimental verification of the prefabricated tungsten sphere fragments driven by TKX-50 and TKX-50+RDX explosives after detonation are carried out under the condition of whether or not there are liners in the high explosive (HE) warhead. The ability of two insensitive explosives (IE) to drive prefabricated tungsten sphere fragments is obtained, and are compared to the warhead performance with JO-8 explosives. The results show that the structural integrity of prefabricated tungsten sphere fragments is greatly improved by adding inner liner in the warhead, and the maximum dispersion velocity of fragments is slightly higher than that of the structure without an inner liner. At the same time, the tungsten sphere fragments driven by TKX-50, TKX-50+RDX and JO-8 explosives can effectively penetrate the preset distance. The ability to drive fragments by three kinds of explosives is basically the same.
Study on Shock Initiation of Covered Composition B by Multiple Fragment Impacts
In order to investigate the interaction between double spherical tungsten fragments and Composition B (Comp B) covered by tantalum coverplates, the numerical simulation was carried out by using AUTODYN-3D software. The influence on the shock initiation characteristics of double fragments at various distance separation b1, time separation h1, impact angle α with the same or different velocities were analyzed, and the critical initiation velocity of covered Comp B was obtained. The obtained simulation results show that, under certain circumstances, the superposition effect of shock waves caused by double fragments impact on covered Comp B is obvious. The critical initiation velocity increases with the increase of b1 when fragments impacting on covered charge at the same time with same or different velocities, with α=0, and approaches critical velocity of a single fragment. The critical initiation velocity decreases initially and then increases with the increase of h1 when fragments impacting asynchronously on covered charge with different velocities and α=0. When fragments impacting synchronously on covered Comp B with different velocities, the critical velocity decreases initially and then increases with the increase of α. When fragments impacting asynchronously on covered Comp B with different velocities, the critical velocity increases with the increase of h1. Therefore, a shock initiation of covered Comp B rather be achieved by multiple fragments at lower velocity than by a single fragment at higher.
Study on Forming and Penetration Performance of Multi-Functional Warhead
Aiming at cruise missiles and anti-ship missiles, a new Multi-Functional Warhead structure was proposed in this paper. With tantalum-2.5 tungsten alloy liner and tungalloy fragments, which could have outstanding penetration ability, through multi-points initiation method, the EFP and fragments were formed in a certain space. Nonlinear dynamic analysis software AUTODYN-3D was used to simulate, and the state, velocity and scattering law of fragments were obtained and verified by experiment. The scattering pattern of the fragments was consistent with the numerical simulation results in experiment, which validated the feasibility of the warhead design. The Multi-Functional Warhead had good application prospect, which could provide guidance for air defense anti-missile ammunition and anti-light armor ammunition of high efficiency damage warhead.
Capability to Absorb Projectile Kinetic Energy by Structures Made in Additive Manufacturing Technology
The paper presents the methodology of designing and testing of energy-absorbing cellular structures made with the use of Additive Manufacturing methods, whose elementary cells are made of struts forming a regular lattice structure. Due to their properties such structures are ideal for use in energy-absorbing structures. As a part of the study, lattice structures (316L stainless steel) in the mesoscale with elementary cells of BCC-Z type were analyzed. Before the tensile tests, non-destructive tests were carried out: photos of the surface with the scanning microscope, photos of cross-sections by means of a computer tomography. Digital Image Correlation method were used for stress-strain curves determination. After obtaining material data, 316L steel specimens of lattice structures with dimensions of 100×100×100 mm and elementary cells of BCC-Z were designed on the basis of numerical simulations. The specimens were subjected to quasi-static and dynamic tests (impact of projectile) and energy absorption capabilities were determined.
Ballistic Efficiency of Lightweight Cage Armor Systems
Cage armor systems similar to the ones used today have been in use since the 1960s and are still being used extensively on many armored vehicles to offer protection against mainly a number of RPG-7 shaped charge warheads. Nevertheless, many misunderstandings still exist up to this day as well as regarding their working principle as regarding their actual efficiency. This article will start by exploring the origins of the current cage armor systems and by explaining the working principle behind them. This will be followed by the development of a methodology to calculate the efficiency of two lightweight cage armor systems (polymer net and inertial distributed weight system) as a function of impact conditions for a specific RPG-7 shaped charge warhead. It will then be applied to these two cage armor systems in order to calculate their overall ballistic efficiency as a function of the compound impact angle.
Comparison of Mine Blast in Water Pit Vs. Sandy Gravel Pit (AEP-55 Soil)
Soil condition, defined by soil type, particle dispersion, moisture content, degree of saturation and other parameters, influence the blast intensity of a buried explosive charge. None of the various existing standards presents an unambiguous uniform definition of soil conditions. While performing a development process, the comparison between the different models is essential, therefore, the repeatability of the test conditions is necessary and critical. In order to eliminate non-tested parameters such as soil conditions, there is a need to use a deployment method that will assure repeatable loading. The most probable way to achieve a repeatable impulse is using a steel pot setup or a water pit setup. Implementing a steel pot for the development phase is the easiest and economical way, however, the impulse half the value when compared to saturated soil conditions. Consequently, as the model does not represent the real test conditions developers may reach erroneous conclusions. On the other hand, the mine blast impulse developed in a water environment is similar to the impulse developed in saturated soil. Furthermore, due to the uniform nature of the water and the fact that the blast is performed in singlephase surroundings, the finite elements calibration process is much easier and more accurate for blasts performed in water setting. As we will show in this paper, a good correlation exists between the field test results and simulation. This can free developers to focus on studying the armor structure or other factors and altogether exclude the influence of the soil parameters from the simulation models. By establishing the above claims, this paper aims to endorse the usage of water pits setup for blast tests, so that most soils conditions can be covered and be reliably repeated during the development process. In this paper, we also present discussion about some physical aspects of the blast in water pit, which may explain the main mechanism that controls the transfer of the impulse from the buried mine to the target structure during the explosion event, and why this explosion can represent fully saturated buried mine explosion.
Parametric Study of Active Counter Impulse Rocket System
IED threats and especially severe blast under combat vehicles are extremely hazardous scenarios, which might occur while performing operational duties. Analyzing armored vehicles structure behavior and limitations undergoing severe blast event show that there are cases when the structure itself sustains the damage and severe plastic deformation, while the passengers may be badly injured as the transferred blast impulse causes high vertical acceleration to the vehicle, resulting in high injury levels to the crew members, especially to their spines. This asymmetry between possible survivability of the structure and poor survivability of the crew, in some cases, is hardly addressed. Plasan R&D team investigates an innovative reactive system, linear rocket motor (LRM™) counter blast system, designed to detect the underbelly explosion and apply a counter-impulse within a short delay (~10ms). Parametric study, including small-scale sample and rocket motors, was conducted with a specially designed rig and a Mine Impulse Pendulum (MIP). The MIP velocity utilizing Counterblast Impulse System was reduced by up to 35% compared with a reference test performed without the LRM™ system. The same conclusion was achieved analyzing numerical simulation of a full combat platform with incorporated LRM™ system. The article presents the methodology for concept validation, describes the test equipment and the test procedure. It is also reviews the simulation work that was done prior to the tests. The discussion about the results includes test data analysis, which was done, based on different measurement methods.
Ballistic Factors of Behind Helmet Blunt Trauma Skull Fracture
Ballistic helmets that defeat the threat can still cause head injuries by striking the head with its backface deformation (BFD). In this study the relationship between kinetic energy (KE), helmet backface response and skull fracture severity in protected post-mortem human subjects (PMHS) and swine was explored. Each surrogate was instrumented with force sensors attached to the skull, fitted with a ballistic helmet and shot. Computed tomography (CT) scans of the post-shot helmet deformation were used to quantify the static BFD depth. When investigating the different fracture severity groups, there were no significant differences in the static BFD depths between severity groups, but KE and BFD velocities were able to distinguish between fracture severity groups. The KE of the incoming round was related to the static BFD depth and BFD velocity, where each increased with increasing KE. This study demonstrates that dynamic metrics of the helmet’s backface response are better predictors of injury than the metrics that are currently used.
A Blockade Effectiveness Assessment Model for Large Navy Ship
The major analytical methods for blockade effectiveness assessment of typical surface targets are Analytic Hierarchy Process (AHP), Fuzzy Comprehensive Assessment (FCA), Grey Relational Analysis and the Delphi method based on expert opinions. Related researches focus on two aspects that adapting the methods for the assessment object, or making reasonable hypothesis to adapt the model for assessment methods. AHP is applicable to the case where there are many assessment factors (indicators) and the assessment conclusion (comment) is given in the form of normalized Judge Matrix; the FCA method is applicable in the case where the comment is fuzzy and the comment is given by fuzzy operation on comment vectors. Current blocking ammunitions to surface targets include cluster munitions, airborne dispensers, etc. In this paper, a cluster munition is selected as the typical ammunition and a large navy ship as the typical surface target. Blockade effectiveness is calculated through Monte Carlo simulation method. The random number method was used to generate the falling point coordinate of munitions and the sub-munitions, and the sub-munitions’ random initiation time. By analyzing the action characteristics of ammunition, the blocking criteria, blocking index and blockade level were defined. Based on what, the performance of current simulation cycle was assessed using an improved assessment method. The single-indicator-comment membership function was constructed by FCA and then the membership of multiple sets of single-indicator-comment was calculated following AHP. After a large number of Monte Carlo cycles, the statistical expectation value tended to be stable. According to Chebyshev’s law of large numbers, the statistical expectation equals to the final blockade effectiveness, which predicts the final blocking performance. The typical ship target and munition were selected and modeled, and then simulated on the MATLAB platform. The sensitivity of the model was calculated, and the calculation results showed that the analytic model was feasible. Keywords: Blockade Effectiveness; Fuzzy Assessment; Analytic Hierarchy Process (AHP); Monte Carlo Simulation
Blast Overpressure Effects of PE4 on a Simplified Rigid Torso
Explosions, whether accidental or intentional, can cause severe injuries and even death. 12% of 4765 patients evaluated from the Joint Theater Trauma Registry, between 2003 and 2006, sustained Primary Blast Injuries, with lung injury resulting in a significant rate of blast mortality. Much of the existing blast injury data, used for the development of injury criteria models, was obtained from animal testing with sheep and subsequently extrapolated to humans using scaling techniques. More recently, mathematical, experimental and numerical models have been developed and employed to investigate blast injury. There are currently three models used for the investigation of blast related injury severity, however the precise physical mechanism which leads to injury still remains uncertain. This study aims to evaluate and compare the results of these three models. In this study, blast tests were conducted using the Blast Test Device and the results were used to predict primary blast lung injury based on a range of blast loading conditions. Firstly, the results were investigated using the Bowen curves to predict primary blast injury. Secondly, injury results for the BTD were calculated using Axelsson and the Injury 8.3 (Stuhmiller) injury prediction program. In general, all of the models predicted appropriate levels of injury for the body and these predictions were comparable to the accepted injury levels for blast loads from 1kg PE4. This study evaluated the three models that predict primary blast injury, an important consideration for the improvement of blast protection as it provided a comparison between the three models.
Multi-Hit Impact Analysis of Ceramic Composite Armours
Modern personnel armour are composite consisting of a front ceramic plate and a backing plate typically made of a metal. In most cases, the armour system needs to be able to maintain its integrity under multiple impacts. A numerical investigation is presented in this work to study the ballistic performance of Aluminum Oxide (Al203) ceramic plates bonded to a backing subjected to multi-hit impacts according the NATO AEP-55 STANG 4569 standard. Numerical models were developed using the explicit finite element code LS-DYNA, which possesses contact, erosion and material failure capabilities particularly suitable for ballistic simulation. The Johnson–Holmquist piecewise linear plasticity and plastic kinematic constitutive material models were used to model the materials behaviors of the ceramic, projectile and backing materials, respectively.
Safety Analysis of PBX Filled Munitions Under Moderate Mechanical Loading
To increase the insensitivity of modern munitions polymer bonded high explosives (PBX) are used more frequently. During launching and impact of munitions the PBX payload experiences dynamical loading conditions with high pressures and high strain rates in the material. These mechanical loads can create through different dissipation mechanisms so called hot spots with subsequent starting of reaction processes and possible final explosion of the confined high explosive (HE). It is a dynamical mechanical loading under pressures (but still significantly lower than typical shock pressure for direct initiation) and shear stresses. The aim of the present work is to characterize the threshold values for onset of reaction in mechanically loaded HE to create a broad basis of experimental data that can be used to improve the physical modelling of these weak reaction processes. For this purpose we developed an experimental set up, the so called safety threshold testing (STT) device and determined in an extensive test series the loading conditions that lead to the onset of reaction processes. Detailed numerical simulations of the performed tests were used to identify threshold values that can be used in numerical simulations for the assessment of munitions safety during military operations.
Analysis of Global Momentum Transfer Due to Buried Mine Detonation
The emergence of improvised explosive devices (IED) significantly extended the spectrum of possible threat mechanisms to military vehicles and their occupants. Especially buried high explosive (HE) charges lead to new and originally not investigated loading conditions during their detonation. The interaction of the embedding geomaterial with the detonation products leads to a strongly increased global impulse transfer on the vehicle, with following high accelerations on the vehicle occupant. This paper presents a comprehensive approach for the analysis of occupant loading. In a first step, we present the so-called ring technology, which allows the experimental determination of the locally resolved specific impulse distribution on a vehicle floor due to buried charge detonation. A complementary method is the use of scaled model vehicles that allows the determination of global vehicle loading parameters such as jump height or vehicle accelerations. Both techniques were used to study the influence of burial conditions as burial depth, embedding material or water content on the impulse transfer onto the vehicle. These experimental data are used to validate material models for the embedding sand or gravel materials. This validated material description is the basis for numerical simulation models used in the assessment of occupant safety. In the last step, we present a simulation model for a generic military vehicle including a Hybrid III occupant dummy that is used for the determination of biomechanical occupant exposure levels. Typical occupant loadings are evaluated and correlated with burial conditions, as HE mass and global momentum transfer.
Experimental Study on Ballistic Performance of Armored Vehicles Against Small Caliber High-Power Projectiles
This study aims to raise awareness amongst armored vehicles developers and manufacturers to reduce the percentage of structural weak areas from the entire vehicle design. Ballistic tests, trials and comparisons were conducted in order to demonstrate suitable solutions to improve the ballistic protection of complete armored vehicles against 7.62 x 51 mm NATO Ball DM111 high-power projectiles. In summary, the percentage of structural weak areas in the rear view of a military vehicle was reduced to over 80% in a modified design compared to the same original design. This was achieved by accurately marking the SWAs of the rear view, then applying some traditional design modifications on weld lines, seams, joints, holes and bolts resulting in an increased protection capability of the vehicle.
Effect of Blast Wave on High Velocity or High Energy Projectiles
Passive armours are the conventional methods used for protection of AFV against high velocity or high energy projectile threats. But due to improvised penetration capabilities of modern projectiles, these passive armours do not meet the expected safety standards. Hence, alternate counter measure mechanisms need to be developed to enhance the protection level. One of the kill mechanism is deflecting the incoming projectile using blast wave. Directed or controlled blast wave is generated, which creates blast wave in close ranges of the projectile. This blast wave intercepts/deflects the path of the projectile. In this paper, finite element based explicit dynamic analysis is done to analyze the effect of two different kill mechanisms of countermeasure against two different projectile threats. Blast wave effect against long rod penetrator and fragmentation effect against high energy (HE) projectiles are considered in the present paper.
Criteria for Selecting Less Sensitive High Explosives to Mitigate Fragment Impact Response
In accordance with MIL-STD-2105D, the United States Army is developing less sensitive explosive and Particle Impact Mitigation Sleeve (PIMS) upgrades to warhead configurations in order to mitigate Fragment Impact (FI) response while maintaining warhead performance. Shock sensitivity as measured by Large Scale Gap Test (LSGT) is often used as a criterion to select explosives for improved munition FI response. This paper discusses recent LSGT and FI testing, utilizing different particle size distribution of LX-14 and PBXN-9 in various anti-armor warhead (AAW) configurations. Results suggest that LSGT alone is not an adequate predictor of FI response, thus requiring an exploration of alternative methods. One methodology of interest, the Small Scale Fragment Attack (SSFA) test, is analyzed herein through a case study as a potential supplement to LSGT.
Preliminary Study for Implementing Head Trauma Risk Assessment into Ballistic Helmets Test Procedures
The importance of studies on behind helmet head trauma is unquestionable and knowledge gained in such research should be consequently used in developing new armour designs and test standards. Current test standards most often measure only two parameters: penetration and backface deformation. The study was therefore performed in an attempt to summarise the state-of-art insight in order to conceive a relatively simple methodology to assess the performance of ballistic helmets in preventing head trauma. The aim was to develop a reliable test methodology, that could be easily adapted in ballistic helmet test standards. The intracranial pressure change was chosen as the measurand. Tests conducted were partially successful. Only one trial resulted in recording proper pressure rise, but the signal registered had clear and significant pulse indicating injury risk. Further analysis of results was made, considering state-of-art knowledge. Also, assumptions were made for future, more accurate research.
Comparison of Selected Operational Characteristics of Classic and Bull-Pup Rifles
Selected results of practical tests of 5,56 mm MSBS (Modular Small arms System) rifles are included within this paper. The main task was to compare operational parameters of standard rifles configurated in different layouts: classic (with butt stock) and bull-pup. It was the first time, such tests were possible since both rifles belonged to the same weapon system. It can be assumed, that all noticed differences are caused by specific layout difference. Practical tests includes typical tactical situation e.g. dynamic firing, changing magazine in different positions and emergency procedures: misfire (dud, failure to feed) and mechanical malfunctions (failure to eject, double feed). The measured parameter was time spent to fire the next shoot. It should be considered that this parameter determines the soldier's survivability on the battlefield. The tests were realized as part of a research and development project No O ROB 0034 03 001 financed by the National Research and Development Centre.
Study on Energy Absorption Properties of High Impact Epoxy Resin/HGB Composites Encapsulating Materials
High performance encapsulating materials for fuze are of vital importance in the process of hard target penetration. This paper studied the dynamic mechanical properties and the energy absorption properties of epoxy resins filled with hollow glass beads (HGB) as the main toughener. First, split Hopkinson pressure bar (SHPB) experiment under different temperature was conducted to obtain the dynamic mechanical properties characterization. Then, the SHPB experiments was modified with short projectile and long specimen with confining pressure to examine the stress attenuation and energy attenuation properties. The stress-strain curve under different temperature was compared and we obtained that the ratio of the peak value of transmitted wave to that of incident wave is about 0.34~0.38, with the corresponding energy ratio about 0.17~0.19. The results showed that the HGB epoxy resin composites is promising potting materials for electronic-packaging survivability of penetration fuze systems.
Integrated Assessment of Ballistic Backface Deflections on Combat Helmets and Prediction of Injury Risks
The presented study includes experimental investigations on dynamic back face deflection caused by ballistic impact on combat helmets and numerical analysis of the effects to the human head. Comparative tests with the measurement system “Pk17dynAâ€ provide the basis for an integrated assessment of injury risks using numerical head model as it is nowadays accepted in other areas like the automotive. Starting from the contact forces obtained experimentally, the performance of three ballistic helmets is evaluated using the FE head model SUFEHM. The simulation results are used for the estimation of risks related to three different head injury mechanisms applying the model-specific injury risk curves. For each of the helmets, simulations comparing the loading with the highest and lowest total force values of a test series are performed, which leads to the evaluation of the potential in injury risk reduction in the context of dynamic deflection of the tested combat helmets.
Terminal Ballistics Application of X-Ray Computed Tomography (XCT) for the Quantitative In-Situ Analysis of Fragments Embedded in Collection Media
The characterization of fragmenting munitions involves conducting arena tests with witness materials (e.g. plywood) to collect fragments. The evaluation of body armour against buried explosives follows a similar process where surrogates made of foam or gel are used to support the armour and capture penetrating soil debris. The manual recovery of the collected fragments is long, tedious and prone to error since small fragments are often not detected. The effectiveness of XCT as a rapid non-destructive technique was evaluated by scanning calibration targets containing various objects of known material types, sizes, and locations. The Fragfinder program was developed to automatically perform 3D images analysis. All fragments were detected and accurately located. For lower density materials (glass, aluminum, titanium), the relative error on the volume of the fragment was within 8%. For higher density materials, (steel, tungsten), larger errors were obtained because of image reconstruction artifacts. Finer reconstruction of target scans using smaller voxel sizes along with artifacts reduction algorithms were explored in order to obtain better precision.
A Preliminary Study into the Effects of 10% Gelatin on RBK Skin Simulant and the Search for a New Zealand Alternative
Skin simulant used in ballistic evaluations should have mechanical properties similar to human skin. It is desired to use synthetic simulants for consistency. The Aim of the study was to determine the if RBK simulant can be utilized n 10% gelatin and if a NZ alternative could be locally sourced. Four simulants were evaluated with 10% gelatin backing: (i) RBK, (ii) NZ Natural Chamois, (iii) Super Cheap Autos (SCA) synthetic chamois, and (iv) SCA Real chamois Testing was carried out to determine the measured V50 of the simulants in comparison to the calculated V50 using a ball bearing with a sectional density of 2g/cm2. From this preliminary study it is shown that for a sectional density of 2g/cm2, all samples evaluated fall within the 35% margin of the predicted V50, however the RBK synthetic chamois is closest to the predicted V50.
Hazard Identification & Risk Assessment (HIRA) for Hypersonic Shock Tunnel and Shock Tube Test Facilities
Shock tubes are the instruments used to replicate and direct blast waves at a sensor or a model in order to simulate actual explosions and their effects, usually on a smaller scale. A shock tube is a simple aerodynamic device that is capable of producing controlled shock waves. Recently many research laboratories all over the world including the Defence organizations have shown special interest in the development of shock tubes test facilities due to its potential applications in aerodynamic testing, material testing, chemical kinetics, biological and Defence & medical applications. Results from shock tube experiments can be used to develop and validate numerical model, materials study, shock attenuation and mitigation, design of blast protective systems etc., Keeping in view of the hazards associated with the operations involved and the recent accidents in the shock tube test facilities, it is paramount important to carry out thorough safety assessment for these facilities to ensure the safety of men, machine and materials inside the facilities. Out of various safety management tools, Hazard Identification and Risk Analysis (HIRA) methodology is best suited for the risk assessment of the shock tube test facility. This paper describes the operation, maintenance safety considerations for a shock tube test facility and also discusses the hazards associated with the facility and suggest suitable hazard mitigation methodologies to ensure safe working environment.
Crush Structures for Attenuating Impact Induced Accelerations
Thin-walled structural members called as crush structures are generally employed in the frontal compartment of road vehicles for absorbing the impact energy by axial mode of plastic deformation which is widely accepted. However, most members demonstrate high initial peak crush forces with equivalent decelerations far above the statutory acceptable limits, low crush force efficiency (CFE) and low stroke efficiency (SE) which affect the overall crashworthiness of the vehicle. This paper proposes few new thin-walled structural configurations with precise distribution of axial stiffness based on numerical procedures. The proposed structural members are aimed at achieving initial peak crush force within acceptable levels of accelerations and improved stroke and crush force efficiencies under pure axial impact. Crashworthiness of these deformable members on various quantifiable parameters is thoroughly investigated and discussed with a recommendation for the best energy absorbing member configuration. The proposed members are made of stainless steel SS304.
Occupant Injury Simulation Using Human Surrogate During Vehicle Underbody Mine Blast Loading
Anti-Vehicle mine is designed to damage or destroy vehicles including tanks and armored fighting vehicles and its occupants. Recent advances in materials have enabled designers to develop mine protected vehicles that can withstand and minimize damage during mine blast. However the occupant safety factor due to tertiary blast injuries in design of mine protected vehicles has been a major concern since experiments in underbody mine blast testing using physical instrumented human surrogates is a costly affair. In the present simulation study a Hybrid III 50th percentile finite element dummy placed inside a vehicle hull is subjected to denotation of TNT using Multi Material Arbitrary Lagrangian Eulerian (MMALE) method. Injury criteria are estimated to evaluate occupant safety. It was observed that the Head Injury Criteria (HIC) and resultant acceleration are within the limit since there was no direct impact of the occupants head. However the compressive loading on the tibia which was directly above the detonation was found to be higher than the safe limit indicating serious injuries to lower extremity. The results provide an insight on the vulnerability of crew seated inside during mine blast loading/
Optimization of Parameters for Blast Inflicted Deflection on Kinetic Energy Projectile
Kinetic Energy (KE) projectiles are major threat to armour fighting vehicles (AFVs). Penetration can be greatly reduced by detonation of a HE charge in the vicinity of the projectile. This can be greatly reduced by transferring momentum from a blast due to detonation of a High Explosive Charge in close vicinity of KE projectile. This blastwill causes a deflection on the KE projectile. The blast can cause deflection of the projectile. The study aims to investigate the effect of explosive quantity, miss distance and intercept distance on the angular deflection of free flying KE projectile. An existing analytical theory based on ideal momentum transfer is available for predicting the deflection of KE projectile using High Explosive charge. The theory is extended and used to estimate the explosive quantity, miss distance, intercept distance and time of initiation of explosive charge, for providing required deflection in KE projectile. Different combination of these parameters are simulated and a set of solutions are discussed and optimised under realistic design space.
New Generation Surface Treatment Techniques for Enhanced Adhesively Bonded Ceramic-Based Composite Armour Systems
Ceramic based armours are of significant importance in ballistic protection systems due to their light weight compared to traditional metallic armour systems. These systems consist of a ceramic strike face bonded to a composite or metallic backing with an adhesive interlayer. In such systems, while the adhesive properties are of great importance, the interface between the adhesive and the materials’ surface must be strengthened to maintain the integrity of the ceramic tiles with improved multi-hit capabilities. In this paper, importance is given to the strengthening of the interfacial bonds by controlling the surface properties using advanced surface treatment techniques leading to enhance ballistic performance of SiC-kevlar armour system. These surfaces are modified by industrially feasible plasma and chemical methods to incorporate large number of high surface energy polar functional groups. These surfaces, bonded with an epoxy and a thermoplastic polyurethane adhesive, showed increased peel strengths and improved performance during multi-hit ballistic impact conditions.
Numerical Simulation Study on the Refrigeration Effect of Air Conditioning in a 155MM Gun
Refers to the operators' safety and comfort in the gun turrets under high temperature environment, it is needed to be equipped with air conditioning to cooling the temperature in the gun turret. In order to study refrigeration effect of air conditioning for the different initial ambient temperature, combined with heat transfer and fluid mechanics theory, the CFD simulation of the refrigeration process was conducted, the temperature change law of time and space was obtained. The results show that, under the effect of air conditioning refrigeration, the turret temperature decreases over time, as the external environment for 60℃, after 1.69 hours, the turret temperature can drop to 30℃. The results of the study can provide reference for the selection of air conditioning in the gun turret and is meaningful for operating personnel safety during the launch.