30th International Symposium on Ballistics
Research on the Effect of Structure Parameters on the Dynamic Characteristics of Terminal Sensitive Projectile
Metal wings are adopted to provide drag force and rotating torque for non-parachute terminal sensitive projectile (TSP). The wings are usually quite thin to adjust the demand for diameter of warhead. It’s conventional to simulate the aerodynamic characteristics by considering wings of TSP as rigid ones. Affected by aerodynamic force, thin metal wings could deflect during the TSP’s falling process, which could affect its aerodynamic characteristics. Therefore it’s more accurate to take wings as elastic body. The wing structure is defined by three parameters including bending angle, bending ratio and length-width ratio. The S-S type non-parachute TSP has two wings which make four bending angles, four bending ratios and two length-width ratios. Based on ANSYS software, this paper analyzes effect of wings structure parameters on aerodynamic characteristics of TSP.
Trajectory Optimization of a Deflectable Nose Missile
The deflectable nose missile has a longer range and higher maneuverability by deflecting its nose to improve its aerodynamic feature. Based on detached eddy simulation (DES), the supersonic flow fields of a missile with deflectable nose are simulated numerically and its aerodynamic force coefficients are calculated under the condition of the deflection angles vary from 0° to 8°, angles of attack, 0° to 8°, and mach numbers, 2 to 5. Coupling these aerodynamic coefficients with the 6 degree of freedom (DOF) ballistic equations, the extended flight range has been calculated. Furthermore, the genetic algorithm (GA) is employed for the solution of maximum range of the deflected missile.
Experimental Study of Low Speed Vertical Water Entry of Projectiles
Experimental studies of the vertical water entry with different head shapes of projectiles were conducted with high-speed camera to capture the cavityrunning phase. To focus on the formation, development and closure of cavity, the projectiles of 90° cone-shaped head, elliptical head and cut-cone head to entry water at a speed of 2.8m/s were used. And the experiments of different speed vertical water entry with 90° cone-shaped head projectile were also conducted. Experimental results showed that there were four types of cavity pinch-off after projectile entered the water: quasi-static seal, shallow seal, deep seal and surface seal. There were two water jets after the closure of splash water curtain; one was upward, the other was downward. The critical water entry speed to occur cavity on the warhead of projectile was 0.64m/s.
Modeling and Control of Supercavitating Vehicle
A supercavitating vehicle dynamic model is introduced based on the piecewise linear planing force function through the nonlinear planing force of a supercavitating vehicle, which is a four dimensional piecewise linear system and its dynamic characteristics (such as the equilibrium point and stability) are analyzed. The controller of the piecewise linear system is designed from the Lyapunov stability theory. It has been found that the controller shows good performance in the process for stabilizing the system and is also applicable for the non-piecewise linear dynamic model of the supercavitating vehicle. By controlling the deflection of the cavitator at the vehicle nose, the stable navigation of the supercavitating vehicle in the longitudinal plane can be achieved.
Test Method Investigation of Trajectory Consistency Based on Damage Efficiency Criterion
For the theoretical and practical problems in ammunition and fuse average trajectory consistency test, starting from basic features of analytical statistics and application characteristics of ammunition, the problems in current test methods were pointed out, such as: the t test method is not used for ammunition with different dispersion, the antiaircraft weapons test does not consider the situation of air shooting, the randomness of test sample size is too big, the evaluation criteria of test results is not reasonable. Improvement suggestion for test method and test point selection is proposed. A new evaluation criteria of average trajectory consistency is put forward based on damage efficiency. By analyzing average trajectory consistency test results of a certain type of armor piercing projectile, prefabricated fragment ammunition and grenade, the correctness and availability of new evaluation criteria is proved.
Ballistic Characteristics of Dual-Spin Projectile with Asymmetric Front Body
Non-axisymmetric arrangement devices in a dual-spin projectile may lead to the asymmetry of the front body, thus affecting the ballistic characteristics. This article presents a 7 Degree-of-Freedom (7-DOF) flight dynamic model which includes a model of additional moment that arises due to asymmetric factors. Two aspects of the ballistic characteristics are studied, namely the first maximum angle of attack and the range of variation. Simulation results indicate that a small asymmetric angle, less than 1 degree, can result in a large change in the angle of attack by up to 6.5 degrees in pitch. But attenuation of the range in the X direction is only 10m. Moreover, when the rotational inertia ratio IA / IF is more than 2, it has little effect on range. The maximum range of attenuation is about 10m at the point where the rotational inertia ratio A F I / I is equal to 1.
Coexisting Attractors in an Underwater Supercavitating Vehicle System
Although supercavity can improve the speed of underwater vehicles greatly, the state of into water and parameters of system often lead vehicles move instability. This paper focuses on this problem. The existence of various coexisting attractors in this system is verified by distribution diagram of dynamic behaviors, and the motion of the vehicle varying with parameters and initial conditions is explored by basins of attraction. The results show that there are a few kinds of coexisting attractors at some parameter combinations of this system, such as two types of stable equilibrium points coexist with each other, a stable equilibrium point coexists with a limit cycle, a limit cycle coexists with a chaotic attractor and a 1-periodic cycle coexists with a 2-periodic cycle and so on, which explain the influence of parameters and initial values on the stability of vehicles qualitatively. In practical application, the stability of vehicles can be improved by setting parameters of system or adjusting initial launching conditions.
External Ballistics and Accuracy of Lead Free Bullets in 5.56x45mm NATO
Several nations have moved to lead free bullets in 5.56x45mm NATO for use as duty ammunition by military personnel. This study reports on the external ballistics and accuracy of two lead free bullet designs that have been fielded to date, the 62 grain lead free hard core bullet manufactured by RUAG and the 62 grain lead free bullet manufactured by ATK at the Lake City Arsenal. Doppler RADAR was used to determine aerodynamic drag curves for each bullet from Mach 1.5 to Mach 3.0 when fired from rifles with twist rates of 1 in 7â€, 1 in 8â€, and 1 in 9â€. Drag coefficients were consistent with claims by the manufacturers when fired from 1 in 7â€ and 1 in 8â€ twist barrels; however, drag coefficients varied up to 50% higher when fired from the 1 in 9â€ twist barrel, suggesting marginal stability. The 1 in 9â€ twist affects the drag of the ATK bullet more than the RUAG bullet. Accuracy of the RUAG bullet was less than 2 minutes of angle (MOA) when fired from a match grade rifle and less than 4 MOA when fired from a service grade rifle. However, accuracy of the ATK bullet was worse (2 MOA to 4 MOA) from the 1 in 7â€ twist match grade rifle and poor (6 MOA to 8 MOA) from a service grade rifle with 1 in 9â€ twist. The original Miller formula for gyroscopic stability of each bullet shows good agreement with experimental data. This formula may be used to estimate gyroscopic stability within 5% for a variety of twist rates, muzzle velocities, and atmospheric conditions.
An Improved Hybrid Extended Kalman Filter Based Drag Coefficient Estimation for Projectiles
An improved hybrid extended Kalman filter (IHEKF) is proposed for drag coefficient estimation from flight data of projectiles. In order to avoid the divergence or even instability in the implementation of HEKF caused by modeling errors and finite precision of digital microprocessors onboard the projectiles, fictitious process noise is added to the system model and covariance matrix is symmetrized at each time step. As a result, the robustness is improved. Finally, simulations are performed and the results demonstrate the effectiveness and superiority of the proposed method.
Experimental and Numerical Analysis of Supersonic Mortar Projectiles
The aim of “Crawfish – Ammunitionâ€ project is to develop supersonic mortar projectile for “Crawfishâ€ (“RAKâ€) self-propelled mortar. This projectile has been developing in Military Institute of Armament Technology. As a main goal of HE projectile is to achieve range above 10000 m, that implicate muzzle velocity according to 500 m/s. Nowadays literature about this kind of projectiles is very poor. In the article authors showed results of exterior ballistic analysis for several types of supersonic mortar projectiles. Analysis was made according to experimental data and numerical calculations. Experimental data was collected on maximum range shooting tests at 500 m/s velocity with 45 degrees elevation. In flight projectile was observed by radar to measure their position and velocity and to gain the data enabled to calculate drag laws for different shape supersonic mortar projectile and quality of projectile stability. Second part of article consists of the CFD numerical analysis of these projectiles. Using Ansys Fluent program authors calculated drag coefficients of these projectiles. Authors estimated the accuracy of CFD method comparing numerical and experimental data. After that they checked drag coefficients of different parts of projectiles (primer, ogive, fins etc.). Analysis of radar data showed drag fluctuations at low velocities of flight (0.5 – 0.8 Ma). CFD method was used to calculate center of force and stability moments. Drag coefficients at different yaw angles was also estimated. That data was used to model yaw of projectiles to compare with experimental data. Finally authors formulated conclusion about accuracy and possibilities of using CFD methods in exterior ballistic.
A Technology of Ballistic Measurement for Multi-Flying Targets
Based on the test requirements of guided rocket, guided aerial bomb and cluster munitions for continuously launching or dropping, a solution of multi flying targets test has been generated by combing techniques of FDMA, GPS and MEMS. The relevant test system has been developed and can be used to test multi flying objects in real time to acquire ballistic parameters including acceleration, angular rate, spinning rate, velocity, position and target’s internal operation signals. These measurement data are transmitted to the ground receiving station by several orthogonal radio channels, then can be processed and analysed for evaluating the dynamic performance of tested projectile. The system composition, operation principle, main specifications and partial test results are described. The results of range test show that the solution is an effective technical approach and has actual application value.
Ballistics of Supercavitating Projectiles
An ordinary gun projectile will, after entry into water, be subject to an extremely high drag and will stop after 50 – 100 calibers of travel through the medium. To avoid such a response, supercavitation must take place. By a specially shaped projectile nose, the flow of water around the projectile may escape contact with the surface of the projectile, except at the nose tip. Under these conditions, the projectile is said to be supercavitating. In such a state, the projectile is unstable, but, the stability is maintained by the oscillation caused by the interaction between the rear part of the projectile and the cavity wall. In order to keep the amplitude of this oscillation as small as possible, the size of the cavity should be just slightly larger than the projectile. The cavity size is, however, determined by the size and shape of the nose tip, by the velocity of the projectile, and by the pressure in the ambient water (i.e. the water depth), through Garabedian’s equations. These parameters will also determine the duration of the cavity which determines how far the projectile will travel before the supercavitation ceases, and the projectile stops. The paper outlines the theory for the size, shape, and duration of the cavity. It discusses also the conditions for designing an optimal design of a supercavitating projectile. Special emphasize is put on how to determine the drag on the projectile by observing the size of the bubble.
Experimental Investigation of Supercavitating Underwater Ballistic Projectile
The ballistic projectile traveling underwater, generally, exhibits severe instability, even if the conventional gyro stability criteria are satisfied. Therefore GSRC has started the research project on supercavitating underwater ballistic projectile, to establish the design method for the simple supercavitating projectile, by gaining the understanding the physics of supercavitation, under the restriction of the compatibility with the conventional gun without special modification. The design method of the supercavitating underwater projectiles was proposed and examined the validity and limitations by the firing tests. The designed projectiles were tested in small scale firing trial into water tank, to validate design method and down select projectiles. The down selected supercavitating projectiles (nose shape, nose diameter and ogive shape) travelled straight down range through the water in firing trial.
Using Forecast Meteorological Data to Reduce the Artillery Error Budget
An unguided Artillery shell fired from guns to ranges greater than 15km can experience significant perturbations that result in large delivery errors. There are a number of sources of error, the largest of which can be the estimation of the meteorological (Met.) parameters along the trajectory (pressure, temperature, humidity (PTU) and the wind vector).
Nonlinear Dynamic Analysis of Supercavitating Vehicles Based on Two-Dimensional Bifurcation
To ensure the steady motion of underwater supercavitating vehicles, based on a four-dimensional dynamic model, the complex dynamical behaviors of vehicles are analyzed by using dynamic analysis tools, the conditions and ranges of variable parameters for the stable motion of vehicles are determined by two-dimensional bifurcation method. And the motion of supercavitating vehicles changing with feedback control gain of fin deflection angle and cavitation number is explored. The results indicate that the dynamical behaviors of supercavitating vehicles not only depend on system parameters, but also closely depend on initial conditions of the system. It can be found some novel nonlinear phenomenon in the system, such as transient period, transient chaos and state transitions and so on. Vibrations and shocks can be suppressed effectively by adjusting fin deflection angle reasonably. The researches have an important guiding significance to the stability control of supercavitating vehicles.
Modeling and Simulation of Interior Ballistics of High-Speed Launch based on Lateral Injection for Energy Compensation Technology
To improve the muzzle velocity by a large margin without increasing the gun chamber pressure, a lateral-injection for energy compensation technology was proposed. The principle is installing a regenerative auxiliary chamber with liquid propellant at a proper location in the barrel to compensate the energy in the space behind the projectile. Aiming at the interior ballistic characteristics of the technology, the corresponding model was established and the numerical simulation was carried out for a certain gun. Results show that the location of the auxiliary chamber, the injection area, the differential ratio and the mass of the injection piston have significant effects on the interior ballistic performance. By optimizing these parameters, the muzzle velocity can be increased substantially. The method can provide a new thought for designing the high-speed launcher.
Simulation Study on Hydrodynamic Cavitation Characteristics of Water Submerged Jet
Waste projectile recycle means a lot to cost saving and could improve the waste propellant utilization ratio. Simulation analysis was conducted to study the emptying technology of waste projectile by cavitating jet. Twodimensional axial model of angle nozzle was build and the cavitating results under different working condition (different inlet media's pressure and temperature, different temperature in the projectile) was simulated by using of mixture multiphase model. The results indicate that, the velocity contours show “sword shapeâ€, and the gas phase mass fraction shows the “tongue shapeâ€ and decay along the axis director. The temperature of inlet media and the temperature in the projectile is not the main factor to influence the cavitation. While the inlet media's pressure affects the cavitation a lot, the bigger the pressure, the better the cavitation intensity. The conclusions could offer references for further study of emptying technology of waste projectile by cavitating jet.
The Projectile Angle Motion Pattern Analysis based on Projectile-Borne Geomagnetic Sensor Test
This article studied the application of geomagnetic sensor in projectile attitude test, by using the dynamic signal data of projectile flight acquired from projectile-borne geomagnetic sensor, combined with projectile attitude motion model, created a method of measuring the projectile-borne geomagnetic signal and acquired the angle motion parameters of projectile in whole trajectory, then acquired the spin angular velocity attenuate law of the projectile and the whole trajectory projectile nutation angle change by analyzing the angle motion parameters. The research shows that the projectile angle motion parameters can be acquired from projectile-borne geomagnetic sensor test, which being comparative analyzed with projectile angle motion characteristics, come to the analysis of the stability and disturbance characteristics of projectile flight.
Fast Perturbation-Compensation-Oriented Trajectory Planning Correction Strategy
An efficient trajectory planning correction strategy and its corresponding algorithm for the glide trajectory of a hypersonic glide vehicle are initially proposed to compensate the deviations due to perturbations which can be determined beforehand. The proposed strategy evolves the traditional acceleration-based trajectory planning into a high-fidelity one with perturbation compensations by correcting the parameters of C1 and C2 , which are named planning data and can modify the drag profile. To derive the mathematic representation of the terminal state deviations induced by perturbations, the ballistic perturbation theory is employed to develop the error propagation model for the glide trajectory. The semi-analytic mathematic relation of the planning data correction quantities and the terminal state deviations are deduced in a “transposed-poleâ€ coordinate system. Taking the gravity anomaly along a glide trajectory which is computed by the 1080-order Spherical Harmonics as the single perturbation factor the performance of the proposed method is validated and verified. The simulation results indicate that the corrected planning outperforms the traditional one, with a reduced terminal positional deviation of about 1km and a nearly twentyfold enhanced terminal precision. The proposed strategy can correct the deviations of any glide trajectories due to arbitrary single/multiple predetermined perturbations efficiently and effectively. The semi-analytic representation of the correction quantities with respective to the perturbations allow it to reveal the error propagation mechanism and thus restrain the perturbation deviations.
Predictions of Coupled Motion Dynamic Derivatives of Projectile
For investigating the aerodynamic characteristics of a novel hedgehopping projectile under the angular motion coupling of pitching and rolling, a method to deal with simulation of the complex angular motion is proposed based on the Euler rotation theorem and sliding meshing technique. By applying this method, and solving and identifying the unsteady aerodynamic parameters, the influences of the projectile’s rolling motion on dynamic derivatives of pitching combination and lift coefficient under various Mach numbers are explored. The results indicate that: in the solving process for the unsteady flow field, the proposed method can eliminate the accumulative errors in calculation of attitude angles effectively, realizing the accurate simulation under arbitrary given angular motion; due to coupling with the pitching motion, the projectile’s rolling motion can generate significant influences on the identification results of dynamic derivatives of pitching combination and lift coefficient, and in details, the identification results always decrease along the increasing the rolling frequency under conditions of different angles of attack.
Improved Theory of Projectile Trajectory Reference Heights as Characteristics of Meteo-Ballistic Sensitivity Functions
Projectile trajectories calculated under non-standard conditions are considered to be perturbed. The tools utilized for the analysis of perturbed trajectories are weighting factor functions (WFFs), which are a special kind of sensitivity functions. WFFs are used for calculation of meteo ballistic elements μB (the ballistic wind wB, the virtual temperature τB, the pressure pB, the density ÏB, the speed of sound a as well. An effect of weapon system parameters can be incorporated into calculations through the reference height of trajectory – RHT. RHT are also calculated from WFFs. Methods based on RHT are far more effective than traditional methods that use weighting factors q. We have found that the existing theory of RHT has several shortcomings due to we created an improved theory of generalized RHT which represents a special sensitivity parameters of dynamical systems. Using this theory will improve methods for designing firing tables, fire control systems algorithms, and meteo message generation algorithms.
Research on the Attack Angle Response of Projectile Considering the Instantaneous and Durable Force Induced by Canards
The investigation in attack angle induced by canards control force is an important issue for trajectory correction technology. This paper focuses on the attack angle response of projectile considering not only durable force but instantaneous force. Following the introduction of the projectile nonlinear dynamic models in the non-rolling reference frame, the equations of attack angle under control are established. The initial angular rate is derived through a model with conservation of angular momentum. The analytical solutions of attack angle under the two conditions are presented. The analytical expression of the relationship between trajectory shift and attack angle is presented. When instantaneous force is taken into consideration, the magnitude of the maximum angle of attack is raised by 10.2%, the steady-state time is extended by 15.2%, whereas the trajectory under two kinds of condition varies little.
An On-Board Recording Technique to Correlate Simultaneous Leeward and Windward Pressure Measurements to Ground-Based Aerodynamic Range Measurements
ARL's recent flight demonstration represents a novel onboard recorder and integration technique that allowed for the first-ever recorded simultaneous measurement of both leeward and windward pressure and ground-based aerodynamic range correlation. Wake flow pressure measurement represents a critical state previously elusive to researchers except for wind tunnels hampered by sting effects or computational fluid dynamics predictions using unverified turbulence models. This paper describes the advancements necessary to further the state-of-the-art capabilities toward readily available and cost-effective research tools and diagnostics. These measurement techniques demonstrate a unique capability to validate models used to design future missions to Mars or the next guided swarm of munitions.
Research on Aerodynamic Characteristics of Trajectory Correction Mortar with Circular Grid-Fin Canard
2D trajectory correction technology has been adopted to improve the accuracy of mortar. The fuze equipped with a trajectory correction canard is a method to achieve effectively 2D trajectory correction. The circular grid-fin has the characteristic of shorter length of fin cell, thereby the flowing choking is reduced effectively. The use of grid fin is well known for its smaller control moments resulting in smaller actuators, which can solve the problem of fuze space limitation. In addition, the circular layout allows it to be closed folded along the surface of the fuze, resulting in little influence on the aerodynamic characteristics of the trajectory correction mortar in the flight before correcting. The computational fluid dynamic (CFD) simulations are carried out to investigate the aerodynamic characteristics of trajectory correction mortar with planar canard and circular grid-fin canard respectively, in the condition of subsonic, transonic and supersonic. Lift coefficients, drag coefficients, lift/drag ration, pitch moment coefficients and center of pressure of trajectory correction mortar with circular grid-fin canard and planar canard are compared. The results indicate the circular grid-fin canard is a good configuration for 2D trajectory correction.
Effect of Firing Conditions & Release Height on Terminal Performance of Submunitions and Conditions for Optimum Height of Release
Aerodynamic Characterization of a New Concept of Long Range Projectiles from Free Flight Data
This paper presents the aerodynamic characterization of a new concept of long range projectile, fitted with six fins. Three distinct projectile architectures were investigated: two with canted fins, while the last one presents twisted fins. The aerodynamic characteristics are determined based on system identification techniques and free flight data obtained by means of different available measurement techniques like radar, magnetometers, accelerometers and 3D high speed optical system. Estimation results from experimental measurements were com-pared to aerodynamic predictions for two configurations investigated.
A Technique to Create Repeatable Yaw in Long-Rod Penetrators
The U.S. Army Research Laboratory recently conducted a set of limit velocity experiments of a long-rod penetrator striking an urban structure with 90o of yaw. In order for these experiments to be successful, the penetrator needed to be pitched to 90o, over a range of velocities, and in a manner where impact location and orientation was controlled and repeatable. This paper presents a method for generating repeatable yaw in a penetrator using aerodynamic forces that does not complicate the terminal ballistic results. The modeling technique used to design the lifting surfaces along with the experimental data is presented.
Perturbation Studies for Separation Dynamics of Store During Release from Aircraft
Store separation dynamics is very crucial from the safety aspects, when the store is released from parent aircraft. The store behavior should not be abrupt in proximity of aircraft. Store separation studies at subsonic release speed are carried out for a canard with tail controlled store with the help of 6-DOF coupled CFD simulations using ANSYS software. Initially, CFD methodology is validated with Eglin Wing Store Separation test case. Then store separation study is carried out for canard-tail controlled store and results are obtained. The estimation of flight parameters (such as CG Position, body attitudes, body rates and store velocity) help to provide adequacy before actual release. However it is difficult to a flight pilot to achieve the specific release flight condition at which the separation studies are being worked out. Therefore it is essential to examine whether the release is safe for those operating conditions which have minor variations over the specified nominal flight conditions as per release envelope. This study is carried out with the help of perturbation analysis to account for variations in input flight conditions. The perturbations studies are time consuming if they are attempted with the help of 6-DOF coupled CFD simulations. However the studies can be easily done with the already available aerodynamic data of specified flight conditions and an offline 6-DOF solver. Aerodynamic data from 6-DOF coupled CFD simulations is post processed using regression analysis to fit the aerodynamic coefficients as a function of separation distance (vertical movement), angle of attack and side slip. An isolated 6-DOF model using MATLAB Simulink is developed. Random variations in release conditions such as altitude, angle of attack, side-slip, center of pressure and Mach number with respect to the nominal operating condition are considered. A Monte-Carlo trajectory simulations are carried out considering above variations and the results are presented in this paper. The band consisting of variations in trajectory parameters is obtained and can be further used to assess the separation dynamics of the store.
The Effect of Humidity on Small Arms Trajectory
With the introduction of handheld electronics, ballistic calculators have become very common. Many smart phone apps and standalone ballistic calculators allow a shooter to calculate the effect of atmospheric changes, along with range and wind, on the trajectory of a projectile. A large majority of these calculation methods utilize a simplified atmospheric model along with simplified trajectory models that reduce the computational burden on the hardware. These models typically ignore the effect of relative humidity on air density. This paper uses a modified 3 degree of freedom (3DoF) point mass trajectory model to examine the sensitivity of a ballistic solution to differences in humidity across multiple temperature ranges. Three common long range shooting calibers are examined across three temperatures. The calibers are .223 Remington, .308 Winchester, and .338 Lapua Magnum. The effect of an accurate humidity measurement on the prediction of the trajectories is shown to be significant. The effect is shown to be dependent strongly on the ambient temperature of the air as well as the target range.
Optimal Design of the Aerodynamic Parameters for the Two-Dimensional Guided Artillery Projectile
An optimization method is introduced to design the aerodynamic parameters of a dual-spin two-dimensional guided projectile with the canards for trajectory correction. The nose guidance kit contains two pairs of canards which can provide lift and despinning with a projectile for stability. An optimal design algorithm is developed to decide the profiles of the steering and spinning canards, and their deflection angles are also simulated to meet the needs of trajectory correction capabilities. Finally, the aerodynamic efficiency of the specific canards is discussed according to the CFD simulations. The simulation and analysis results can be further applied to the exterior ballistics design.
Determination of Aerodynamic Co-Efficients of Fin Stabilized Armour Piercing Penetrator using Yaw Cards
The main battle tank, form one of the most important, and at the same time most difficult, groups of targets to be defeated on the battlefield. The modern development of anti armour kinetic energy projectiles has been in the direction of long rod and fin stabilised penetrators. This configuration is very much sensitive for in bore balloting and perturbations during discarding of sabot. These disturbances mainly affect the lethality due to sinusoidal motion of penetrator in its flight. FSAPDS (Fin Stabilised Armour Piercing Discarding Sabot) ammunition is the Primary Ammunition for all kind of tanks. Design of ammunition with minimum yaw plays an important role in achieving desired lethality and goals. The experimental data was utilized with a mathematical model to determine aerodynamic coefficients of penetrator in flight.
Computational Analysis of the Aerodynamics of a Bending Body Projectile at Supersonic Speeds
Computational fluid dynamics is used to investigate a bending body projectile as an alternative control methodology to improve gun-launched projectile maneuverability over that of a canard-controlled projectile in the supersonic regime. A fin-stabilized projectile of length-to-diameter ratio 10 is considered. A feasibility study analyzes the aerodynamic performance of a dual bent-body (8° bend at nose-body junction and 8° bend along the body) compared to the straight body and a straight body with 4-10° deflected canards over a range of Mach numbers and angles-of-attack. The resulting aerodynamic coefficients reveal that a projectile that cruises in a straight-body configuration and changes into a bent-body configuration for maneuver control is likely to provide greater control authority than a canardcontrolled projectile. An optimization study seeking to optimize the bentbody geometry of the Air Force Finner for maximum control authority and minimum drag is initiated.
Numerical Techniques for the Prediction of the Aerodynamic Behavior of a Complex Projectile
Aerodynamic coefficients are predicted by traditional, uncoupled computational fluid dynamics (CFD) and coupled CFD/rigid body dynamics simulations on a complex, canard-controlled projectile. The projectile is considered in its uncontrolled state as well as for canard deflection angles such that pure pitching motion is induced. Static and dynamic aerodynamic coefficients are considered for each of the component contributions (i.e. body-fin with interference effects and individual canards). For the non-deflected canards, the aerodynamic model is equally well described by either method. The coupled simulations are completed in roughly the same total CPU time with greater angular resolution than the traditional, uncoupled CFD. For the cases with deflected canards, the traditional, uncoupled CFD was able to isolate additional dependencies: (1) angle of attack as well as canard deflection angle dependency for the body-fin interference effect, and (2) a deflection angle as well as a local angle-ofattack dependency on the canard aerodynamic coefficients.
Ar-15 Barrel Motion as a Function of Weapon Mount Configuration
In the field of experimental small arms ballistics there has always been a large amount of energy put into how a test weapon is secured. Various philosophies exist; however, this is largely left to experience and is more of an artistic approach rather than a scientific approach. Many experimentalists leverage physical understanding of the firing event to reduce motion or vibration. However, in most cases, there is no direct measurement of the performance of the mounting technique. Often the dispersion performance of a weapon system when fired from a specific mount is used as a gauge, ignoring the fact that dispersion is comprised of many sources. Through complex jump testing, the US Army Research Laboratory has shown the ability to dissect the relative contribution of individual dispersion sources. This work showed that it is possible to mount a weapon system in a way that barrel motion does not affect the dispersion or jump behavior. This effort employs an easy-to-use modern measurement technique to characterize barrel motion of a commercial AR-15 weapon during dispersion testing. High speed digital micrometers were used to measure barrel motion before, during, and after firing in order to establish the pointing angle and crossing velocity variability as a function of mounting configuration. Ten mounting configurations were examined for a single weapon type firing match grade ammunition with the intention of isolating the barrel motion effects.
Prediction of Spatial Distribution of Fragments from a Preformed Fragmentation Warhead using Mathematically Constructed Model
This paper presents a novel technique for modeling and prediction of spatial fragment distribution of preformed fragmentation warheads. Using this technique, the distribution of fragments in various angular zones is generated using a mathematically constructed model, in which each fragment is represented by a 3-D coordinate with respect to a specified coordinate system. These coordinates are generated in the form of circular arrays of fragments stacked one after another and following the contour of the warhead along the longitudinal axis. Fragment ejection velocity is computed from Gurney's equation for cylindrical warheads. Fragment ejection directions are assumed to be distributed normally around the mean ejection direction, given by Shapiro's formula, for each circular array. Standard deviation of distribution is estimated by minimizing error in average simulated fragment distribution with respect to average fragment distribution data obtained from experiments.
A Statistical Method for the Evaluation of Projectile Dispersion
As part of a research program, an extensive study on the dispersion characteristics of eight different 7.62×51 mm ammunition types was conducted. The paper presents the main steps in the experimental and analytical process carried out to evaluate, namely to measure and compare, the dispersion characteristics of the ammunitions; namely, (1) identify the number of rounds to fire in the trials, (2) establish a test plan and the setup for the precision trials, (3) fire the rounds, following an established protocol for the experiments, (4) collect the impact points, and measure the performance through statistical measures, (5) perform a statistical analysis of dispersion applied to the results obtained in the trials, and (6) conclude on the ammunition characteristics. In particular, the paper proposes a statistical method to evaluate the precision of ammunitions fired with precision (Mann) barrels. The practical method relies on comparison of confidence intervals and hypothesis testing on the standard deviation of samples, namely the impact points. An algorithm is proposed to compare the variances of two or more populations of ammunitions.
Probase: a Software Application to Estimate Drag in Base Bleed Technology Units using Large Eddy Simulation
Base Bleed is a widely used technology to reduce the drag of bodies in flight such as in the case artillery projectiles. It is based on increasing the pressure at the rear of the body through the injection of a low velocity fluid. In this paper we present a new PC application called “PROBASEâ€ developed by EXPAL Systems SA and the Technical University of Cartagena (UPCT). The application, based on Qt® and OpenFOAM® and with a user friendly “interfaceâ€, is able to estimate drag coefficients of slender bodies with Base Bleed units. This estimation is performed through the simulation of flight conditions and the resolution of the Navier-Stokes equations of the flow field with AUSM schemes and Large Eddy Simulation turbulence models. In the presented version, the transient computations are done with an axisymmetric two-dimensional approach of the problem, zero angle of attack and a fixed Base Bleed mass flow rate and swirl. Validation against experimental data is also included.
Modeling and Simulation Studies for Advanced Towed Artillery Gun System
Ever increasing needs of modern artillery for increased range, accuracy and automation led to a new Towed Artillery Gun System (TAGS) development by Defence Research and Development Organisation (DRDO), Ministry of Defence (MoD), India. Modeling and simulation studies were carried out, to determine the essential ballistic performance parameters are presented here. Various subsystem configurations involving existing, modified and evolving technologies were studied so that a suitable design configuration is identified for development of the gun system. The adopted approach assumes possible near-time and far-time realization of each constituent & contributing subsystem’s maximal performance. The overall emphasize has been on realizing a weapon system, which fairly matches the performance dictated by the systems world-wide at the lower end of the operational spectrum and would also offer enhanced performance at its higher end. Comparable performances have already been demonstrated for ammunition systems like M90 Modular Charge System (MCS) and Extended Range Full Bore (ERFB) class of projectiles. Further enhancement to performance is expected with alternate charge designs and/ or process-modified ammunition systems. Future enhancements to range performance is likely to be realized with ongoing developments in projectiles, charge systems and Course Correction Fuzes (CCF). System studies with modeling and simulation for subsystem analysis & evaluations have resulted in a base-line parameter set. A solution with reduced iterative design & development life cycle has been conceived and had been realized. 155mm/52 cal Advanced Towed Artillery Gun System (ATAGS), realized with base-line design parameters has successfully demonstrated muzzle velocities of order ~1010 m/s with seven Higher Zone (HZ) M92 modules of M90 MCS at ambient Mean Sea Level (MSL). This has lead to enhanced ranges of +35km and +45km with ERFB-Boat Tailed (BT) & Base Bleed(BB) shells respectively, against 29km & 39km with six HZ modules of MCS for comparable systems world-over. Further enhancements with CCFs and Velocity enhanced Artillery Projectiles (VLAP) are being attempted to realize a range of +60km with increased accuracy.
Projected Area and Drag Coefficient of High Velocity Irregular Fragments that Rotate or Tumble
3 degrees of freedom (DOF) exterior ballistic computer models are used in fragment studies to calculate individual trajectories of each fragment based on drag coefficient and the projected (presented) area in the direction of velocity of center of mass. The expectation of a randomly distributed projected area is commonly used for fragments that tumble (random rotation) during flight. We forecast a model where the expected drag coefficient is dependent of shape and Mach number. Rotation or tumbling only affects the expected projected area. Models of projected areas during tumbling and rotation are presented. An examination of the data by McCleskey (1988) indicates that the volume of the fragment to the power of 2/3 is a better parameter to characterize the drag coefficient of the fragments than the maximum projected area. Hydrocode simulations are used to verify results and to study projected area and drag coefficient of fragments.
Influence of Silencer Use on External Ballistics of Projectiles
The following article is a summary of the first step of research on behavior of sniper rifles in calibers .308 Winchester, .300 Winchester Magnum and .338 Lapua Magnum with and without sound suppressor. The paper includes measurements of chosen external ballistics parameters like velocity and accuracy at 300 m (328 yd) with the use of state of the art electronic devices like high speed accuracy light gates and Doppler radar system. The paper includes also a comparison of mentioned parameters registered during testing with two types of silencers and with unsuppressed weapon. The paper is concluded with results analysis that can be used for future work.
Influence of Muzzle Devices use on Accuracy of Competition Weapons
The following article is a summary of the comparison testing of small arms weapons used in sport competition (IDPA, IPSC etc.). The test includes GLOCK 19 and 19C pistols, AKMS rifle and Heckler & Koch 416 rifle with and without an underslung grenade launcher and covers the accuracy testing of a weapon with different muzzle attachments. The shooting was conducted in a dynamic shooting manner with double taps and triple taps by a highly trained shooter. The measurements were conducted with high speed accuracy light gates. The paper is concluded with a summary and proposals for future expansion of this topic.
Trajectory Tracking Study based on Integrated Guidance and Control
For gliding range-extended rocket, the range-extending problem is translated to tracking issue against gliding project trajectory. Integrated guidance and control method is studied aiming to improve the tracking performance of classic guidance and control law. Firstly, the study problem and background are introduced in the introduction part. Then the models of rocket dynamics, relative kinematics between the rocket and target, integrated guidance and control are all established in the second part of this paper. In the next two parts, the integrated guidance and control law is designed based on ADRC and compared with the classic method through mathematic simulation. The classic method uses PID control law and PN guidance law. Simulation result shows that the integrated method can deal with greater disturbance and can effectively improve the quality of dynamical response.
An Aerodynamic Shape Optimum Study for Long-Range Guided Rockets to Maximize the Range and Increase the Hit Accuracy
In order to obtain the optimal aerodynamic shape parameters of long-range guided rockets (LGR), an optimization model of LGRs’ aerodynamic shape is established. To design a guided rocket for the maximum range and best-hit accuracy, a shape optimization system is combined with an exterior ballistic analysis and optimization technique. In the flight section, the aerodynamic coefficients are calculated in every time step with a semi-empirical method and connected to the motion equation of the guided rockets. Monte Carlo method was applied to simulate the disturbance in flight to obtain the average range and CEP. In the optimization section, a real-coding genetic algorithm was adopted to find out an optimum shape of the multi-objective: best lift-drag ratio, maneuverability and stability. The shape optimization system of a long-range guided rockets can maximize the range under certain hit precision and provide the optimum shape and installation location of canards, tailfins and nose. The analysis results confirmed that the optimum shapes extended the range of the basic shape by 9%, and increase the circular error probable (CEP) by 14.8%.
Simulation Studies for MRSI of Artillery Gun Systems
Artillery’s ever-increasing quest to deliver more payloads to the target, with the surprise element of attack in tact is un-satiable. Time-on-target (ToT) fire plans have been in practice with battery fire to meet this requirement to certain extent. Multiple Round Simultaneous Impact (MRSI), is an extensions of this methodology to a single gun system. Employing more prevalent multiple charge options through Modular Charge Systems (MCS), and ammunitions would largely benefit artillery fire schemes in realizing this goal. The advent of developments in ammunition handling, auto loading, auto laying and ballistic computing capabilities of modern artillery systems further paves the way closer towards achieving this feature. Near real time ballistic computation is an essential component in providing MRSI solutions. Although effectiveness of MRSI depends on a number of key parameters, it can be lumped in to a single parameter like Time Between Consecutive Fires (TBCF), which is the algebraic sum of time required for ordnance laying, projectile-load-ram and charge load, breech close, primer insertion operations. Factors like elevation & azimuth traverse rates, increased rate of fire, reduced projectile loading restrictions, availability projectile and charge mix available, all significantly influence the key parameter TBCF. A study to assess the technical feasibility of this capability with various 155mm family of weapon systems with constituent subsystem has been undertaken. MRSI concept modeling & simulation studies that have been carried out for 155mm ordnances considering 5/6/7 charges modules of 39cal/45cal/52cal respectively with standard ERFB-BT ammunitions are presented here. This study was applied for assessing the feasibility and for establishing the enhanced effectiveness of MRSI for 155mm/52 cal Advanced Towed Artillery Gun System (ATAGS) of DRDO, MoD, India. Expected performance of the system is also presented briefly here. The measure of effectiveness of MRSI can be aptly specified by, total no of rounds, in a range bracket within specified impact tolerances over range, line and time. ATAGS is with elevations varying from 0 deg to 73 deg and employs M90 Somchem BMCS from zone-1 to zone-7 along Naschem ERFB shells. With a TBCF ~6.5 sec it is expected to deliver 5 rounds at a range of 20km. A capability, which arguably depends on various subsystem’s coordinated and timely functioning. This feature would illustrate the artillery weapon system’s all round performance in terms of agility brought about by automation.
Validation of the NATO Armaments Ballistic Kernel for Use in Small-Arms Fire Control Systems
In support for the development of a new small-arm ballistic computer based on the NATO Armaments Ballistic Kernel (NABK) for the Canadian snipers, DRDC Valcartier Research Centre was asked to carry out highfidelity 6 degree-of-freedom (6-DOF) trajectory simulations for a set of relevant vignettes for the snipers, and to compare the direct fire 6-DOF simulation results with those obtained with the 4-DOF NATO Armaments Ballistic Kernel (NABK) adapted to simulate small-arm ammunition trajectories. To conduct this study, DRDC Valcartier Research Centre used BALCO v1.0b. This paper presents (1) the process and the methodology employed to carry out the sniper direct fire solution study, (2) the modeling and the simulation of the sniper projectile, the approach used in calculating the firing solutions, and the results of direct fire simulations for the sniper vignettes, and (3) an analysis of firing solutions obtained with the BALCO engine versus those of NABK. The work presented in this paper serves to validate the use of NABK for the new sniper ballistic computer.
Flight Mission Sequence Optimizer for Vulcano
The Vulcano Guided ammunition family can engage short, medium and long range targets, using the canards to extend the ballistic range and guide precisely on the target. The smartness of the ammunition allows to engage the same target following different paths, characterized by different Quadrant Elevation of the gun and other mission dependent parameters. An optimal solution is defined as the solution, among the possible, with the highest accuracy and flight robustness in respect of scenario unknowns. The optimizer of the FMS is software that identifies automatically the best firing solution for the Vulcano ammunition also in presence of scenario constraints (i.e., aerial corridors, far crest near crest).
Experimental Investigation on Ignition Characteristic of NEPE Propellant
The ignition characteristic of solid propellant is the main content in internal ballistic research. In this study, the factors which may have an impact on ignition delay time of Nitrate Ester Plasticized Polyether Propellant (NEPE) are analyzed by a CO2 laser radiation experiment. Using high-speed camera, the ignition process of NEPE propellant is recorded under different environmental conditions. Results show that the ignition delay time decreases with the increase of laser heat flux, ambient pressure and initial temperature of NEPE propellant. At the same time, with the increase of laser heat flux, the influences of ambient pressure and initial temperature on the ignition delay time decrease. Besides, the effect of oxygen concentration on the ignition delay time is confirmed that the oxygen content has little effect on the ignition delay time when the oxygen content of the ambient gas is less than that of the propellant pyrolysis product.
Ignition and Combustion of Pyrotechnics at Low Pressures and at Temperature Extremes
Rapid and effective ignition of pyrotechnic countermeasure decoy flares is vitally important to the safety of expensive military platforms such as aircraft. QinetiQ is conducting experimental and theoretical research into pyrotechnic countermeasure decoy flares. A key part of this work is the development and application of improved models to increase the understanding of the ignition processes occurring for these flares. These models have been implemented in a two-dimensional computational model and details are described in this paper. Previous work has conducted experiments and validated the computational model at ambient temperature and pressure. More recently the computational model has been validated at pressures down to that equivalent to 40,000 feet but at ambient temperature (~290K). This paper describes further experimental work in which the ignition delays of the priming material in inert countermeasure decoy flares were determined for pressures down to 40,000 feet and at temperature extremes of - 40ºC and 100ºC. Also included in this paper is a comparison of the measured and predicted ignition delays at low pressures and temperature extremes. The agreement between the predicted and measured ignition delays is acceptable. This paper is an extended abstract – the full paper appears in Defence Technology, Volume 13, Number 3.
Headspace Effect on Aluminum Cartridges Case Behavior
Aluminum cartridge case has long been considered as the alternative material for brass cartridge. It can efficiently reduce the weight carried by soldiers, help soldiers carry more ammunition with the same cartridge case, and thus improve the combat effectiveness. However, Aluminum cartridge case can be broken off during the course of use, which is a common phenomenon. By using the finite-element method, the paper is intended to analyze the effects on the deformation of cartridge case, the position and magnitude of maximum strain with the headspace variation law ;the maximum headspace of aluminum cartridge; the simulation result that maximum headspace indeed causes break is also verified by the firing experiment.
Solid Propellant Burn Rate Measurement in a Micro Closed Bomb
In the present work experimental data from seven perforated (7PF) JA2 propellant combustion in a micro closed bomb is presented and the linear burning rate of the JA2 propellant is determined. The burn rate measurement is based on a sophisticated lumped parameter model which accounts among other things for arbitrary cross sectional propellant geometries with the help of the ICT-Cellular-Combustion-Algorithm (ICCA), pressure dependent thermophysical parameters and heat loss. The model is used to construct a vivacity based objective function which depends on the parameters of the empirical law for the linear burning velocity. With the Nelder-Mead downhill simplex optimization algorithm the objective function is minimized and the burn rate parameters determined. The comparison of the results to published data show that with the new burn rate measurement method the linear burning rate can be determined with great accuracy even when only a few propellant grains with a total propellant mass of less than 8 g per shot are used.
Analysis of Dynamic Vivacity Curves Obtained on the Basis of Valved Closed Vessel Test Data
This work is a continuation of the research presented at the 29th ISB, concerning an analysis of the dynamic vivacity function determined on the basis of closed vessel tests results. The main conclusion of the analysis was that the form of the vivacity function strongly depends on the loading density. In order to analyze this dependence for the loading densities ranging from 300 to 700 kg/m3, the valved closed vessel (VCV) was used. The maximum value of the time derivative of pressure was attributed to the end of the pyrostatic period. The dynamic vivacity curves for this period were determined. The strong dependence on the loading density was revealed. This was explained by differences in the temperature distribution inside propellant grains. The effect of this distribution on the values of the burning rate was analyzed. Conclusions concerning the method of analyzing closed vessel test data were formulated.
Preparation and Study of Ultrafine Flake-Aluminum with High Reactivity
To achieve aluminum particles with ultrafine granularity and high reactivity, the mechanical ball-milling method was adopted and three kinds of coatings, including stearic acid (SA), viton (F) and dinitrotoluene (DNT), were added. The effects of milling time and different coatings on granularity and reactivity of ultrafine aluminum particles were studied. The structures of prepared ultrafine aluminum were characterized by scanning electron microscopy, X-ray particle diffraction and the thermal properties were analyzed by TG/DSC. Besides, the reactivity of prepared ultrafine aluminum particles was comprehensively analyzed and judged according to several thermodynamic parameters, the maximal oxidation rate, the oxidation degree of aluminum and the enthalpy change. The results revealed that aluminum particles prepared by the mechanical ball milling method were all flake-like and the particle sizes were below 5 μm with nanometer-scale thickness. And the crystal form of aluminum was found to be unchanged. Besides, the ultrafine flake aluminum coated with stearic acid after milling for 5h showed the highest reactivity with 56.1% of oxidation degree (α) before 660 ℃, 0.945 mg/℃ of maximal oxidation rate (νox) and 20491 J/g of enthalpy change (ΔH).
The Influence of Nozzle Diameters on the Interaction Characteristic of Combustion-Gas Jets and Liquid
To investigate the controlling method of interior ballistic stability of bulk-loaded propellant guns, the combustion-gas generator and cylindrical stepped-wall chamber are designed aiming at the injection processes of combustion-gases in liquid. The expansion courses of Taylor cavities and the turbulent mixing characteristic of gas-liquid are recorded by means of high speed photographic system. Based on the experiment, three-dimensional unsteady model on the interaction of gas and liquid is established to simulate expansion characteristics of twin combustion-gas jets in liquid under different nozzle diameters. The distribution regularities of characteristic parameter in jet field are obtained and analyzed. The results show the pressure, velocity and temperature distributions under different nozzle diameters are basically the same at the initial time. As time goes on, these characteristic parameters under different nozzle diameters have large differences.
Research on the Deformation of Die Pins during Propellant’s Extrusion Process
The phenomenon that the holes change the position caused by the pins moving exists in 7-perforation propellant extruded by the solvent mothed. In this paper, the analysis of the forming process based on fluid-structure interaction method of mode pins moving was studied. The pressure distribution of extrusion process was analyzed and the effect of temperature and velocity on the pins deformation was analyzed. Three dimension video microscopy was used to measure the web sizes of the propellant grains. The results show that maximum deformation of die pins present a quasi-linear increase trend with the speed increase. When the entrance velocity is faster than 0.4mm·s-1, increase rate of deformation is reduced. Deformation presents linear decreasing trend with the propellant dough temperature increase. The Nitroguanidine propellant is extruded by seven-perforation die in different experiment conditions. The experimental data and numerical simulation results fit well.
Numerical Analysis of the Internal Ballistic Properties of Underwater Launched Gun with a Gas-Curtain
When the gun submerged underwater is launched, the gun barrel is filled with water, which leads to much higher resistance in front of the projectile than that launched in air. So, the projectile acceleration decreases and the chamber pressure increases sharply so as to result in a burst barrel phenomenon. Base on this research background, this paper proposes the gas-curtain launch of underwater gun. Through a tiny hole opened in the projectile head, the powder gas is guided to inject into the front of the projectile to drain off water, which contributes to create a gas environment for projectile flight in the tube. Thus, the resistance before the projectile decreases to control the chamber pressure and improve the muzzle velocity. The paper designed a projectile with a central orifice for the 12.7mm machine gun and established the mathematical physical model for the gas-curtain launch to simulate and investigate the internal ballistic properties. The computational results show that, the gas-curtain launch of underwater machine gun can be achieved with appropriate variable-burning rate powder. Taking the internal ballistic performance of gun launched in air as reference, the underwater gas-curtain launch shows superior performance than the fully submerged underwater launch when the same charge quality is employed. The maximum chamber pressure and the muzzle velocity under the gas-curtain launch respectively are 86.5% and 81.6% of the situation launched in air, while the chamber pressure rises sharply to 298.9% and the muzzle velocity decreases to 71.2% under fully submerged underwater launch. The internal ballistic performance can be improved by adopting appropriate ventilation mass flow rate of 75.3 gïƒ—s-1, which can ensure the fully expand of the gas jet to create a gas channel with lower pressure. At this time, the maximum chamber pressure can decrease to 85.2% while the muzzle velocity can rise to 85.5% of the gun launched in air. It can be found that the present gas-curtain launch for underwater gun can effectively improve the internal ballistic performance and it has vital academic and practical value.
Synthesis and Performance of Insensitive Ladder-Like Nitrocellulose
The study of insensitive explosives and propellants has been receiving intensive attentions from the investigators. Nitrocellulose is a primary composition of high energy propellants. Due to its high sensitivity to external stimuli, many researches try to reduce its sensitivity to increase its security performance. In order to prepare the insensitive nitrocellulose, the step ladder-like nitrocellulose was synthesized by isophorone diisocyanate reacting with free hydroxyl groups of nitrocellulose first, and then reacting with the polyethylene glycol. The product was characterized by FTIR, SEM, TG, DSC and sensitivity test, respectively. Results show that the nitrocellulose is modified with polyethylene glycol successfully, and its morphology changes from the rod-like to the globular. Besides, the step ladder-like nitrocellulose has more moderate decomposition process and lower sensitivity with respect to the raw nitrocellulose.
Experiments and Numerical Simulation on the Expanding Processes of High Pressure Hot Gas Jet in Bulk-Loaded Liquid
An experimental system, which was composed of a high-pressure gas jet generator, transparent chambers with various interior geometries and a high-speed video recorder, was built for the investigation of interactions between high-pressure gas jet and bulk-loaded liquid. A gas-liquid two-phase turbulent flow model was also developed. The experimental and calculated results indicated that in the multi-stage stepped-wall combustion chamber, the two-phase flow was induced by the step, the radial expansion was enhanced and the axial expansion was retarded, thus the Taylor-Helmholtz instability which generated due to the effect of shear at gas-liquid interface decreased. The chamber geometry and the jet intensity had evident effects on the jet expanding and turbulent mixing processes. The presented work is helpful to better understand the physical processes of combustion gas expanding in bulk-loaded liquid.
Simulation of Two-Dimensional Interior Ballistics Model of Solid Propellant Electrothermalchemical Launch with Discharge Rod Plasma Generator
The full paper is published in Defence Technology(10.1016/j.dt.2017.05.004). Instead of the capillary plasma generator (CPG), a discharge rod plasma generator (DRPG) is used in the 30mm electrothermal-chemical (ETC) gun to improve the ignition uniformity of the solid propellant. An axisymmetric twodimensional interior ballistics model of the solid propellant ETC gun (2D-IBSPETCG) is presented to describe the process of the 30mm ETC launch. The 2D-IBSPETCG model includes: pulse forming network (PFN) discharge model [3,4], DRPG model and 2D two-phase flow model.
Applied Analysis of Electrothermal Chemical Launch Technology in 155mm Modular Charge Howitzer
Based on the research of large caliber modular charge howitzer and electrothermal-chemical (ETC) launch technology, the application advantages and prospects of ETC launch technology in a 155mm modular charge howitzer are discussed from the perspective of the technology development and actual applications, respectively. The analysis and discussion results show that the ETC launch technology will effectively improve the chamber combustion stability and interior ballistics consistency of the modular charge howitzer. It also will enhance the whole operational effectiveness including both firing range and accuracy. The ETC launch technology is an important development route for the future modular charge howitzer.
Research Progress of Pressure Testing Technology for Electrothermal-Chemical Launch
A strong electromagnetic interference is always appeared in electrothermal-chemical launching process. Several charging and discharging of high voltages can cause the ground voltage floating. These often produce a serious impact on the nearby testing devices, influence the measurement accuracy of the bore pressure, and even damage the measuring equipment. In the last dozen years, three kinds of pressure testing schemes are designed, which one is the on-site storage measurement, another is the dual insurance measurement technology that combined the site storage measurement with digital fiber communication technology, the third is the real-time measuring system of in-situ distributed test and remote synchronization detection for electrothermal-chemical gun (ETCG) chamber pressure. The pressure test system is gradually perfected, which can solve the problem of EMI, and the multi physical parameters (plasma load voltage and current, bore pressure, muzzle pressure and muzzle velocity signals) are unified in the same time axis.
Preparation and Performance of Insensitive Spherical Nano-Sized Nitrocellulose
The sensitivity study of energetic materials has been the focus of research interests, and a great deal of achievement has been gained in this field of energetic materials other than nitrocellulose. Recently, energetic thermoplastic elastomers have been used as binders to replace nitrocellulose to prepare the insensitive high-energy propellants. However, these binders still have some defects. Preparation and application of insensitive nitrocellulose may overcome these drawbacks. In order to reduce the sensitivity of nitrocellulose, the spherical nano-sized nitrocellulose was prepared by pretreatment, degradation and nitration of cellulose. Products were characterized by TEM, XRD, TG, DSC and sensitivity test, respectively. Results show that the prepared nano-sized cellulose is spherical particles with diameters in the range of 15-30nm. Contrast with the traditional nitrocellulose, the spherical nano-sized nitrocellulose has more moderate thermal decomposition process and lower impact sensitivity.
Research on the Influence of Augmented Rail Length and Charging Voltage to System Launch Efficiency
For an electromagnetic launcher (EML), a time-varying current will generate the electric induction force. Moreover, magnitude of the electromotive force depends on the location, speed, and acceleration of the armature. For the series augmented (EML) in the initial part of barrel, the distribution of inductance gradient is influenced by the length of the augmented rails. Besides, both electromotive force and inductance gradient are essential factors to the launch efficiency. For a specific rail structure and time-varying current, the augmented rail length should be optimized to maximize the launch efficiency. In order to research the influence of the augmented rail length to the launch efficiency, a calculation model considering contact resistance, electromotive force and friction force is employed and modified. The model consists of a pulse-forming network power supply (PPS) system and an augmented launcher. By changing the length of the augmented rail, a series of parameters are obtained involving inductance gradient distribution, induced force etc. Based on the results, the efficiency and energy loss distribution are analyzed. Furthermore, the relationship between rail length and launch efficiency is acquired. The results can be used to optimize the railgun design.
Factors Determining Nature of Dynamic Vivacity Curve During Closed Vessel Investigations
It is assumed that the mechanism of gun propellant gases production is dependent on the knowledge of propellant grains geometry and adoption of a geometric model of propellant grains burning. In the paper, the authors analyse the influence of arrangement of propellant grains in a combustion chamber on the changes of dynamic vivacity. The grains of the propellant charge have been piled up spontaneously at the bottom of a combustion chamber or have been spaced separately, systematically on the whole circuit of a combustion chamber. The investigations were carried out with application of black powder ignition and gas ignition for the same loading density. The results of closed vessel investigations showed that the character of dynamic vivacity is determined not only by geometry of propellant grains but also by the conditions of heat transport between hot ignition gases and available burning surface of propellant grains.
Response of Nitramine and Non-Nitramine based Composite Propellant to Pulse Triggered Combustion Instability
Combustion instability (CI) is a major concern during design and development of propulsion system for various rockets & missiles. This work aims to investigate effect of nitramine on combustion response of low alumunised composite propellant. To study the CI, two different propellant compositions with and without RDX were analysed for their response to ejecta using ejecta pulser. The ejecta pulser injects the teflon ball or ejecta in solid rocket motor which may trigger CI in the motor or in worst case may result in catastrophic motor failure. Both the motors were pulsed at 65% of burn time. The response of the motor to this pressure pulse was analyzed and quantified in terms of rate of change of acoustic energy (αM) which determines the stability of motor. The αM values for propellant compositions with RDX and without RDX were found to be +17.69 and +31.47 respectively which shows that the nitramine based composite propellant are less susceptible to combustion instability as compared to non-nitramine composite propellant.
The Study of Abnormal Combustion Light Gas Guns
The combustion light gas gun (CLGG) uses combustible low molecular weight gas as propellant to burn, expand and propel the projectile out of the barrel with higher muzzle velocities. Previous researches had revealed that the deflagration to detonation transition (DDT) process easily occurred in oxy-hydrogen mixture. The great energy released detonation can cause the bore premature accidents. Large eddy simulation (LES) methodology and a detailed chemistry model with 9 components of 18 reactions are applied to investigate the process of flame acceleration (FA) and DDT in CLGG. The mole concentration ratio of oxy-hydrogen gas mixture plays an important role on the interior ballistic process, especially the phenomenon of DDT. Therefore, some typical simulation cases with different charging ratios are carried out to study the abnormal combustion process in the chamber so as to direct the safety operations in experiments.
Experimental Study on Continuous Rotating Detonation Engine
In order to study the detonation stability of continuous rotating detonation engine, an experimental study was carried out on three annular slots of different area ratios, using hydrogen as fuel and air as oxidant. Based on the high frequency pressure signal, the influence of the annular slot area ratio on the detonation parameter stability was analyzed. The experimental results show that when the area ratio is 0.08, the detonation wave propagates in a double-wave colliding mode, and the peak pressure is in the range of 0.3-0.9MPa. When the area ratio is 0.16, the detonation wave propagates in single wave mode, and the pressure peak is around 2.0MPa. When the area ratio is 0.32, the detonation wave propagates in a single-wave/double-wave coexistence mode, and the peak pressure fluctuation ranges from 0.4 to 3.0 MPa. When the area ratio is 0.08, the detonation wave self-sustaining propagation stability is strong, but the detonation wave stability is weak when the area ratio is too large or too small. Therefore, the area ratio of the annular slot has a great influence on the mixing effect of hydrogen and air, which consequently impacts the detonation stability of the continuous rotating detonation engine.
Studies on Composite Solid Propellant with Trimodal Ammonium Perchlorate Containing an Ultrafine Fraction
Composite solid propellant is prepared using tri-modal Ammonium perchlorate (AP) containing coarse, fine and ultrafine fractions of AP with average particle size (APS) 340, 40 and 5 μm respectively, in various compositions and their rheological, mechanical and burn rate characteristics are evaluated. The optimum combination of AP coarse to fine to ultrafine weight fraction was obtained by testing of series of propellant samples by varying the AP fractions at fixed solid loading. The concentration of aluminium was maintained constant throughout the experiments for ballistics requirement. The propellant formulation prepared using AP with coarse to fine to ultrafine ratio of 67:24:9 has lowest viscosity for the propellant paste and highest tensile strength due to dense packing as supported by the literature. A minimum modulus value was also observed at 9 wt. % of ultrafine AP concentration indicates the maximum solids packing density at this ratio of AP fractions. The burn rate is evaluated at different pressures to obtain pressure exponent. Incorporation of ultrafine fraction of AP in propellant increased burn rate without adversely affecting the pressure exponent. Higher solid loading propellants are prepared by increased AP concentration from 67 to 71 wt. % using AP with coarse to fine to ultrafine ratio of 67:24:9. Higher solid content up to 89 wt. % was achieved and hence increased solid motor performance. The unloading viscosity showed a trend with increased AP content and the propellant couldn’t able to cast beyond 71 wt. % of AP. Mechanical properties were also studied and from the experiments noticed that % elongation decreased with increased AP content from 67 to 71 wt.%, whereas tensile strength and modulus increased. Burn rate increased with increased AP content and observed that pressure exponent also increased and it is high for the propellant containing with 71 wt.% of AP due to increased oxidiser to fuel ratio. Catalysed composite solid propellant is prepared by using burn rate modifiers Copper chromite and Iron oxide. Addition of Copper chromite and Iron oxide has enhanced the burn rate of tri-modal AP based composite solid propellant. The catalytic propensity of copper chromite is higher than that of iron oxide. The pressure exponent increased with the catalyst concentration and the values obtained are compatible for solid rocket motor applications.
Electrostaticspray Preparation and Properties of RDX/DOS Composites
Composite explosives based on 1, 3, 5-trinitro-1, 3, 5-triazinane (RDX) with dioctyl sebacate (DOS) as desensitizer were prepared by electrostatic spray method. After preparation, particle size and crystal structure of the composites were characterized, and the chemical features, such as chemical bonds, functional groups, thermal decomposition parameters and mechanical sensitivity, were investigated as well. In terms of the morphologies of the composites, the particle sizes are in the range from 1 μm to 3 μm. Compared with RDX, the crystal types, chemical bonds and functional groups of RDX/DOS composites are unchanged. The activation energy of the composites is lower than that of raw RDX, and the 3wt % DOS composite has the lowest activation energy. The impact sensitivity and friction sensitivity of RDX/DOS composites are lower than those of raw RDX, and the 10wt% DOS composite has the highest H50 (125.9 cm) and the lowest friction sensitivity (8%).
Research on the Damage Diagnosis for Rails with a New 3D Scanning Method
During the process of railgun launching, due to the large current across the interface between the rails and the armature, a series of damage phenomena, i.e. gouging, edge erosion, deposition, etc., will be appeared on the rails. Those phenomena not only shorten the rails’ lifetime but also affect the interior ballistic performance. Therefore, to understand the effect of these different forms of the rail degradation, it is necessary to obtain the surface geometry appearance of the rails. A new three-dimensional surface scanning technology based on the binocular stereovision theory is proposed to adapt complex in-bore environment. Verification experiment shows that this surface scanning technology is feasible, but still needs improvement.
Effects of Baffle Plate on Flow Field and Performance of Two-Phase Pulse Detonation Engines
In the present work, computational investigation was performed on a gasoline/air PDE with and without baffle plates. The size of baffle plate was varied in order to investigate the effects on the characteristics of flow field from the exit of PDE. The conservation element/solution element (CE/SE) method using adaptable unstructured meshes was derived and applied to calculate the inner and outer flow fields of multi-cycle two-phase PDE with and without baffle plate. The computational results of inner and outer flow field show the effects of baffle plate on the shock wave propagation.The existence of baffle plate can reduce the upstream pressure disturbance of PDE. It’s beneficial for the protection of the key composition of PDE.
Research on the 3D Reconstruction for Railgun Bore Scanning Based on Combined Binocular Vision and Laser Marking
There are complex morphology features caused by some phenomenons(like ablation, abrading, planing, aluminium deposition, and shape changing) during the railgun launching. And the features are important to the research of rails’ high life research, efficient armature, and internal trajectory. This letter designs a scanning method by combining laser marking and binocular vision. Through the laser marking system we can mark the target by a large scale laser dots. And the depth information of the feature points is calculated based on the binocular vision. A proper angle between the two image acquisition devices makes the close distance measurement done, thus we may realize the 3D reconstruction of railgun. In this letter we analysis the accuracy of the method and conduct a confirmatory experiment, which prove that this method can make a pretty accuracy and efficiency 3D reconstruction of railgun.
Integrated Optimization Design of Interior and Exterior Ballistics of Cased Telescoped Ammunition Gun
Aiming at the object of the firing range maximization of the grenade of the cased telescoped ammunition(CTA) gun, a classical interior model was established according to the special charge structure of the CTA and the principle of the sequential combustion with two ignitions. Combined with the particle trajectory model, the optimization design of the integration of the interior and exterior ballistics was carried out using the intelligent optimization algorithm. The results show that, the maximum chamber pressure and the muzzle velocity simulated using the interior model of the CTA gun agree well with the experimental results. The optimal scheme of the projectile mass and the charge design was obtained by means of the optimization design of the ballistic integration. The grenade projectile mass increases 16.4% and the maximum range increases 11.8% compared with the original scheme. The method in the paper can improve the integrated ballistic performance of the CTA and provide an efficient tool for its ballistic and charge design.
Simulation Analysis of Closed Combustion Process of Low Temperature Hydrogen-Oxygen Premixed Gas used in CLGG
Low temperature hydrogen-oxygen premixed gas was used as fuel in the combustion light gas gun (CLGG). At the beginning of the study, closed burner was adopted as analog device of CLGG to study the combustion properties. Combustion light gas gun (CLGG) uses lowtemperature hydrogen-oxygen premix gas as a working fluid. In the early stages of research, a closed burner was used to study the combustion characteristics. Finite-rate chemistry model was used to simulate the combustion process of the low temperature (190K) hydrogen-oxygen premixed gas in closed burner. Mass ratio of hydrogen-oxygen premixed gas was 1:2 and the contours distribution of the pressure, temperature and vapor fraction in the device was got. The results show that, in the closed burner, lots of heat was generated as the mixture gas was lighted. And then the combustion gas expanded and vibrated in the finite space which caused the pressure wave. Results of the study could offer references for the controlling of the CLGG combustion.
Study of Characteristics of Burning Rate of Propellant at Different Charge Zone for Large Caliber Artillery Gun Systems
In order to get the different muzzle velocity in large caliber artillery gun systems, the propellant charge usually have several charge zones. When these charge zones been fired, the different chamber pressure and projectile velocity will happen which can influence the burning rate of propellants. It is very important for getting the burning rate of propellants in different charge zone when predicted the performance of interior ballistics. Usually we can get the burning rate of propellant from experiment results of closed bomb, but these results cannot be directly used in numerical simulation of interior ballistics processes for all charge zones. Now, we use a serial experiment of gun firing for different charge zone to get the performance of interior ballistics. On the basis of the simulation for performance by the IB code, we can get the real burning rate of propellant in IB processes. By using the methods, we can get the accurate results for predict the interior ballistics performance when different charge zones were used. So in this paper, an approach has been developed for getting the real characteristic of burning rate of propellant at different charge zone for large caliber artillery gun systems.
Theoretical Analysis on the Effect of Burning Rate of Combustible Cartridge on Interior Ballistic Performance
Combining the results of combustible cartridge and propellant in closed bomb, the classical interior ballistic theory was used to calculate interior ballistic process of the charge with combustible cartridge. The influence of burning rate of the combustible cartridge on the interior ballistic performance parameters was studied. The matching relationship between the burning rate of the combustible cartridge and the different charge structure is confirmed, which provides references for the design of interior ballistic and charge structure.
Analysis on the Influence of the Resistance of a Projectile on the Pressure Distribution in the Gun
In order to study reason of the barrel damage, one-dimensional two-phase flow trajectory model was used to study the pressure distribution law in the gun, to study the movement law of the projectile with different resistance in the bore and the pressure distribution. Effects on the tube strength and projectile strength are also studied, to provide a reference for the analysis of the cause of the barrel damage.
Combustion Performance of the Multi-Perforated Gun Propellants and Influence on the Interior Ballistic Performance
To study the combustion rules of multi-perforated gun propellants, the closed bomb test of 19-perforated grain gun propellants and stick gun propellants and curve-cut stick gun propellants was accomplished. Combustion rules of the gun propellants in different pressure were concluded according to analyzing the data of test. The results also show the effects on the propellant combustion performance caused by different type size. A combustion model of 19-perforated curve-cut stick gun propellants was built by researching the change of combustion rate in the process of burning in the chamber. The results of the closed bomb test were used in an interior ballistic model of those propellants. The model was used to calculate different ballistic schemes to study that how the propellants with different combustion performance affect the interior ballistic performance. The calculation model was proved to be feasible by comparing the simulated results of one scheme with the results of ballistic gun test.
New Launch Principle Artillery with Single Chamber and Multiple Barrels
This article describes new launch principle artillery, which consists of one chamber with multiple barrels. On the basis of the idea, the author establishes the interior ballistic model and the hit rate model of artillery, analyzes and calculates the interior ballistic performance, exterior ballistic performance and hit rate of the artillery. According to the analysis, compared with the traditional artillery, single chamber multi-barrel artillery(SCMBA) can improve the muzzle velocity and hit rate of artillery at the same time. The main reason is that the ratio of the chamber volume and projectile mass improves greatly, so the pressure curve decline becomes more gently, to help improve the muzzle velocity. The other hand, the projectiles have the same muzzle velocity, with a parallel trajectory, reach a predetermined location at the same time, and form dense intercept barrage, which is conducive to intercept missiles or other high-speed aircraft.
Two-Dimensional Numerical Investigation of the Influence of Axial Length on Continuous Rotating Detonation Engine
To study the characteristics of flow field in combustion chamber of continuous rotating detonation engine (CRDE), based on Two-dimensional Conservation Element and Solution Element (CE/SE) method, the numerical simulation was carried out to the effects of combustor axial length on the flow fields and propulsive performances of CRDE. Results show that the CE/SE method is quite efficient to capture the detonation wave. The flow field structure of the combustor is qualitatively consistent with the experimental results of kerosene/air/oxygen mixture detonation. With the increase of the axial length, the length of oblique shock wave and the average values of the axial velocity increase, while the fluctuation at exit, the peak values and average values of the exit pressure and exit density decrease. In addition, the peak values of the axial velocity rise first and then fall, and the circumferential velocity decreases. With the axial length increasing, the flow field needs more time to reach quasi-steady state, the specific impulse first increases and then remains constant.
Experimental Investigation of Compressive Mechanical Properties and Fracture Mechanism of AP-HTPB Base Bleed Grain
The compressive mechanical properties of hydroxyl-terminated polybutadiene (HTPB) bonded ammonium perchlorate (AP) base bleed grain (BBG) was studied via quasi-static (8.3×10-5~8.3×10-1s-1) and split Hopkinson pressure bar (SHPB) experiments (1200~6600s-1) conducted at 28℃. Scanning electron microscope (SEM) was used to examine the fracture patter after dynamic experiments. All non-linear stress-strain curves consisting of linear elastic and post yield region indicate that strain rate has a significant effect on the mechanical properties. Original damage evolves at low strain rate because there is difference between true stress - true strain curves from the first and the second time of quasi-static compression tests. Hysteresis loop exists in loading and unloading procedure and it is clear that strain energy is dissipated in the form of thermal energy in the period of compression. The maximum deformation is up to 0.6 during quasi-static and SHPB experiments. The main fracture mechanism changes from dewetting to matrix tearing and AP fracture when the strain rate increases to 6600s-1 in SHPB experiments.
The Research on Engraving Process of 12.7 mm Projectile
The engraving process of projectile is very complicated process and play a key role on the ballistic performance. To get more insight into the behavior of the engraving process, this paper presents research on the interaction between small caliber projectile and rifling barrel with Quasi-static push test. The resistance force was measured during the projectile engraving process from the forcing cone under different barrel temperature. The push force vs. travel was recorded for the projectile transition through the forcing cone. The experiment results show the barrel temperature are important factor on the engraving force of the small caliber projectile.
A Comparative Study of Combustible Cartridge Case Materials
Foamed combustible material based on polymer bonded RDX was fabricated using CO2 as foaming agent. The inner structures of felted and foamed combustible materials were presented by SEM. The two materials presented different formulations and inner porous structures. The combustion behaviors of felted and foamed materials were investigated by closed vessel test. Simultaneously, the co-combustion behavior of combustible cartridge case with 7-perf consolidated propellants was also investigated. The results of closed vessel test is applicable to gun system which is made of the foamed combustible material as component.
Research on the Criterion of Transition for Electromagnetic Launching
In this paper, the multiple factors in the transition process is comprehensively analyzed. When the armature is sliding at a very high speed, the velocity skin effect will generate the melt-wave. Then the melt-wave will produce a reversed electromagnetic force, which will leads to the armature separating from the rail. The larger the erosion area, the stronger the separating force. Besides, the mechanical force is much smaller than electromagnetic force. When the contact area cannot meet the conductivity capacity of large current, there will appear transition. The prediction formula of transition is given. The calculation results are almost in consistent with the experimental data. Finally, this paper proposes a key criterion coefficient of j2V, defined as the transition criterion. From the quantitative analysis and experimental data, its value is about 4E20 (A/m/s). When the contact power is greater than this criterion coefficient, there will be transition. It makes the prediction to be more convenient and quickly, which will be very useful for the railgun design.
An Approach for Optimization of the Wall Thickness (Weight) of a Thick-Walled Cylinder under Axially Non-Uniform Internal Service Pressure Distribution
Today, improving the weight/load carrying capacity ratio of a part is the matter of studies in most of the scientific and industrial areas. Autofrettage dimensions, the amount of material removed from outer and inner radius while manufacturing and the service pressure applied affect the residual stress distribution throughout the wall thickness and hence the load-bearing capacity of a thick-walled cylinder. Calculation of residual stresses after autofrettage process and optimization of autofrettage outline dimensions by using the amount of service pressures applied are common issues in literature. In this study, mandrel-cylinder tube interference dimensions were renovated by using traditional methods for swage autofrettage process of a gun barrel. Also, the residual stresses in the cylinder after autofrettage process, inside and outside material removal process and the variable service pressure throughout the cylinder applied were taken into consideration and incorporated into the design. By using the constrained optimization method, wall thickness (thus the weight) was optimized (minimized) to achieve the specified safety factor along the length of the cylinder. For the same cylinder, the results of the suggested analytical/with residual stress calculation approach were compared to analytical/without residual stress calculation results and numerical topology optimization method calculation results. Since the experimental measurement results are not yet available, it was not possible to compare them with the calculation results. The suggested approach enabled 22.9% extra weight reduction in proportion to numerical topology optimization and enabled 4.2% extra weight reduction in proportion to analytical/without residual stress optimization. Using this approach, the gain from residual stresses after autofrettage operation, the loss of residual stresses after material removal, and the effects of service pressures can be taken into account for each stage of design.
This paper investigated the effect of mid-wall water cooling for the gun barrel under continuous firing. A 2D cross-section model of the gun barrel is adopted and the cooling channel is circular. An interior ballistics code is used to determine the inner wall convection boundary condition, providing gas temperature and heat transfer coefficient. Results of temperature histories of the inner wall and outer wall and temperature distributions are presented. The results show that this cooling method can slow down growth rate of the peak temperature of the inner wall.
A Series of BKNO3 Nitrocellulose based Low Sensitivity Igniters with Varying Ignition Characteristics
In this effort, a series of BKNO3 and nitrocellulose based igniters were formulated. Their thermodynamic output and gaseous properties were calculated. Their laboratory scale sensitivities were demonstrated to be significantly better than that of benite. Their performance characteristics based on closed bomb were evaluated and compared to that of both black powder and benite. These new igniters are more akin to benite in terms of relative force, and are quite varied with regard to relative quickness and relative vivacity. These new igniter formulations will provide gun system designers a means to vary the brisance and speed with which an igniter exerts its mechanism of action on the propellant, thus allowing them to tailor the ignition system through choice of material.
Developmental Challenges during Realization of High Progressivity Rocket Motor
High Progressivity Rocket Motors (HPRM) are designed to eject an article out of a tube. High burn rate, progressive burn pattern, small burn time and low area expansion ratio are peculiarities of the motor. Initial 200ms of burn time are critical for functionality of motor whereas the test results showed deviations and pressure jumps in first 200ms. The performance further deteriorated when tested after conditioning at higher temperature. The motor test results were studied. Gas flow velocity characteristics inside individual port were studied and found to be on higher side even though the erosive burning constant ‘g’, [1], when calculated, was found to be within limit as specified for normal burn rate motors. Motor configuration was modified to reduce flow velocity and flow interaction. Modified configuration, when tested, was as predicted without any pressure jump. After comparing the flow characteristics, limits for velocity and ‘g’ values were reestablished.
Investigations of Inhibitors for Double Base Propellants by the Use of Real Time Roentgenoscopy
In this paper the results of investigations of double-base propellants covered by inhibitors are presented. The method of Real Time Roentgenoscopy (RTR) has been applied to the studies. This method enables the observation in the real time the burning process of the propellant grain being located in subscale rocket motor. Performed tests allowed to confirm the influence on the burning process of solid propellants are having defects of different kind of the inhibitors. Among the effects, the acceleration of the burning process of propellants was observed as a result of growing the burning surface. This effect resulted from improper adhering of the inhibitors to the surface of propellant or the discontinuity of the structure of the inhibitor. The results obtained in these experiments allow in the simple way to assess the practical suitability of the new kind of inhibitors. The applied testing method allows also to get information about effectiveness of inhibitor functioning of rocket propellants after the long term storage.
Obtaining a Correlation between Pressure Test Results of Small Caliber Ammunition According to Different Test Standards
The science of “Internal Ballisticsâ€ have extensively studied the pressure generated within the cartridge and clearly indicate that maximum generated pressure (Peak Pressure) is not to exceed the yield strength of the material of which the cartridge case is made of [1]. Failure to ensure this could result in catastrophic accidents that may lead to death or serious injuries. Different test standards (SAAMI, C.I.P, MIL-STD and NATO EPVAT) were established to ensure the safety of the ammunition in terms of pressure. These standards differ in many aspects from the test procedure to the equipment used to the acceptance criteria. The main motive behind this study was understanding the need to establish a scientific correlation between pressure measurements obtained by different test standards in order to save cost, time and effort as well as ensuring that a specific type of ammunition that was pressure tested according to one standard is safe to use in a specific weapon that was tested according to another. The main aim of this study was to investigate the possibility of finding a scientific correlation between the mean peak pressure values obtained by the NATO EPVAT and CIP test standards for 7.62 x 51mm NATO Ball Reference Ammunition through derived and validated equations with fixed conversion factors in order to convert “actualâ€ Mean Peak Pressure (MPP) and Standard Deviation (SD) values obtained by NATO EPVAT test to predict those values in the C.I.P equivalent and calculate the Average Maximum Pressure (Ptmax).Thirty 7.62 x 51mm NATO BALL reference ammo were tested according to NATO EPVAT and C.I.P and the mean peak pressure conversion factor (FMPP) was found to be 0.974, while the standard deviation conversion factor (FSD) was 1.381. Both conversion factors were used to convert the MPP and SD values obtained by EPVAT testing of the reference ammunition, to their C.I.P Equivalent. These C.I.P converted values were then used to calculate (Predict) the Maximum Average Pressure Ptmax which was 3540.26 bar. Validation of this result was achieved by conducting an actual C.I.P pressure test on the same amount of reference ammunition which resulted in a Ptmax of 3422.40 bar with an error percentage between actual and predicted Ptmax of 3.54%.
Modifying Small Caliber Interior Ballistics by Employing a Flash Tube
Small caliber interior ballistic performance can be altered in countless ways. Primer composition, propellant composition and quantity, as well as the interaction between the two play a critical role in determining a cartridge’s performance. This study will focus on the interaction between the primer products and the ignition of the propellant of a 7.62- mm cartridge. To accomplish this a flash tube will be employed to alter the ignition characteristics of the propellant. By employing a flash tube the primer products will be directed into the case at a more forward location in the propellant bed thus altering the ignition and subsequent burning characterization of the propellant. Various length and diameter flash tube configurations will be explored to characterize how the ignition of the propellant influences the interior ballistics of the cartridge.
Ballistic Properties of Nitrocellulose based Propellants after Artificial Ageing
It is a characteristic property of nitrocellulose-based propellants that the nitric ester constituents e.g. nitroglycerin, nitrocellulose, undergo a slow decomposition even in ambient temperatures. The degradation products formed, unless removed, can cause a reduction in chemical stability which can lead to cook-off / self-ignition due to the exothermic nature of reactions involved. In addition, they can lead to a loss of calorific value, changes in ballistic properties and cracking in large diameter charges. It is very important to control gun powder after artificial ageing of the parameters such as: burning behavior (linear burning rate and the pressure exponent), stabilizer depletion and content of the nitric oxide. Our work consisted accelerated ageing of different kind of nitrocellulose based propellants according to STANAG 4620 (AOP 48). The next step was to provide the research of ballistic (ballistic bomb) and chemical properties (High Performance Liquid Chromatography).
Optimizing the Form Function of Gun Propellants
Progressivity, i.e. gain in burning area, of multi-perforated propellant grains is graphically shown to have a maximum for certain dimension ratios. Form functions, amount of slivers, and optimum dimensions for some basic grain types are presented. The effect of finite manufacturing precision on form function, progressivity, and amount of slivers is estimated approximatively. This study of form functions is strictly geometric, no physical effects of combustion, like flame spread, combustion inside perforations, or erosive burn rate, are taken into account.
Laboratory Tests of Pyrotechnic Delay Ignition used in the Rockets Motors
The article features several methods of the pyrotechnic delay ignition (PDI) laboratory tests. PDI is used as an ignition source in rocket motor. PDI is used in the projectile with assisted rockets or antitank rocket projectile. The task of the PDI is to ignite the rocket motor with a certain time delay at a given distance from the projectile launch. Therefore, a proper operation of PDI affects the reliability of the ammunition and, above all, the safety of the shooter. The article describes the construction of the PDI and the pyrotechnic delay charge (PDC) – the main component of the PDI was outlined. Then several types of laboratory tests in different variants were carried out. In the tests a CO2 laser, the high speed camera and the optical and acoustic sensors were used. The authors also proposed a new method of the PDI research, which uses the real time radioscopy (RTR) with the possibility of observing the images in real time. The advantage of the RTR method is the possibility to observe the combustion front in the PDC. The received results were verified to evaluate different types of the laboratory tests.
Developments in Additive Manufacturing of Energetic Materials at TNO
Since common energetic materials are not easily compatible with existing additive manufacturing techniques, the Energetic Materials department of TNO in the Netherlands worked closely together with the Additive Manufacturing and Material Solutions groups of TNO to develop new types of energetic material that can be processed in standard 3D printers, aiming at better performance and greater flexibility in the manufacturing of energetic products. This contribution gives an overview of potential applications for additive manufacturing of energetic materials, ranging from rocket propellants to explosives, gun propellants, and other applications. The paper then briefly describes TNO’s research efforts since 2013 into AM of energetic materials. Next, the work performed on additive manufacturing of gun propellants, using stereolithography, is described in more detail, including the results of the material development and characterization, and performance test results, including test firings with a 30 mm gun. The paper concludes with an overview of the current status of the research at TNO, as well as a definition of the next steps to be taken and a vision of the future of additive manufacturing of energetic materials.
Testing of Homogeneous Rocket Propellants by the Use of Real Time Roentgenoscopy
This paper describes a method allows to check the constancy of burning surface area of homogeneous propellant grain located in subscale rocket motor. Observations were conducted with the use of X-ray system, contained the X-ray tube and the semiconductor detector or analog detector coupled with Phantom high speed camera. This system gave the possibility of recorded up to 300 frames per second. Analysis of individual photographs enabled to get to know of stability and speed of the burning process and also shape of the burning surface area. The applied testing method allowed to get information on the character of the combustion process of the new kind of rocket propellants and rocket propellants after the long-term storage.
Skin-Core Structure Gun Propellants with High Combustion Progressivity
Skin-core structure propellants were fabricated using chemical foaming agent AIBN. The thickness of skin and the apparent density of foamed propellants decreased with the foaming agent amount from 0.92 mm to 0.51 mm, 1.35 g/cm3 to 0.79 g/cm3, respectively. The burning characteristics of foamed propellants with skin-core structure were investigated by closed bomb test and the results showed that the skin-core structure propellants having the appropriate skin thickness have an advantage of burning progressivity. Simultaneously, there was an apparent transition point between the combustion of solid skin and foamed core, the transition pressure increased with the increased skin thickness.
Study on the Performance of a New Propellant
A new propellant was prepared from the base propellant grain by impregnation with the blasting oil, followed by deterring with the deterrent in water medium. The combustion performance of this propellant was investigated by means of closed-bomb test and interior ballistic test. The barrel erosion was characterized by erosion test. It is found that this propellant burns more progressively and the value of Pr increases from 0.035 to 0.445 when compared with the base gun propellant. The interior ballistic performance for this propellant charge is improved obviously and the muzzle velocity increases by 5.0% from 886.6 m/s to 931.3 m/s. This propellant has the characteristic of low temperature sensitivity at the same time. The barrel erosion of this propellant decreases by 16.3% at least. This new propellant has the advantages of higher combustion progressivity, higher muzzle velocity, low erosion and low temperature sensitivity.
CFD Study of Seal Groove during the Mortar Interior Ballistic Process
To avoid gas escaping from the gap between tube and projectile in mortar, some seal grooves structures are designed. The blow-by phenomena should be considered in the simulation of interior ballistics. In order to investigate the gas leakage, computational fluid dynamic study of seal groove during the mortar interior ballistic process is presented in this paper. By the seal groove, the pressure near the outlet decreases directly. The mass flow rate of the structures without seal groove and with seal groove at the inlet are similar. However, the mass flow rate of the structure without seal groove at the outlet is obviously bigger than that of structures with different seal grooves. The results show that the seal groove such as trapezoid seal groove can decrease the gas leakage and improve the interior ballistic performance. The further study on structure optimization will be a reference for the mortar design.
Impact Disrupted Gunshot Residue: a Sub Micron Analysis Using a Novel Collection Protocol
In this experiment, silicon substrates were used to collect gunshot residue (GSR) fired from rim-fire ammunition were analysed under cold Filed Emission Gun Scanning Electron Microscope with an X-flash Energy Dispersive X-ray detector. This allowed for particle analysis throughout individual particles at great resolution. During this analysis, different populations of particles of an irregular and molten-looking morphology were discerned, indicating that particles upon impact, forming "impact disgruntled" GSR.
Enhanced Propellant Performance via Environmentally Friendly Curable Surface Coating
(Full Manuscript submitted to the Defence Technology Journal) Surface coating of granular propellants is widely used in a multiplicity of propellants for small, medium and large caliber ammunition.
Performance Predictions of Liquid Fuel Ramjet Combustor
rotating parts. Free stream air is compressed in the intake due to ram effect and allowed into a combustion chamber, where fuel is mixed and combustion takes place. Hot gases, after combustion are exhausted through a convergent-divergent nozzle, generating thrust. Liquid Ramjet (LFRJ) combustor is presently being developed at DRDL, Hyderabad. In order to establish ignition and flame stability of the ramjet combustor, initial design of combustor with four circular intakes is realized and tested. Using the experimental data, CFD analysis was carried out and found that the results obtained from the CFD analysis are in good agreement with that of the experimental values. Various designs of LFRJ combustors are analyses using CFD and the best with 90% C* efficiency is recommended. Proof hardware is realized and tested in connect pipe mode. The engine has been static tested maximum for a duration of 40 seconds wherein stable combustion and flame holding is observed. The combustion efficiency is around 90%. A number of static tests were conducted simulating Sea Level, 5km and 10 km altitude conditions and the flame holder has sustained combustion for these altitude conditions.
Design of a Pulsed Solid Propellant Divert and Attitude Control System (DACS)
The End game for a kill vehicle of Hit-to-Kill Missile is very critical, as it depends on its variable divert and attitude correction capabilities. A Solid DACS provides quick reaction propulsion that positions the vehicle to intercept its target. The Pulsed Solid DACS provides propulsion for control error correction and for vehicle maneuvering. The attitude control systems (ACS) have six thrusters to provide roll, pitch and yaw control. These thrusters act synergistically and precisely aim the vehicle seeker to properly view the target. The four divert thrusters provide short/ long pulses to quickly and accurately position the kill vehicle for a collision with target. A high burn rate propellant is used to meet the divert and attitude control thrust requirement. Four divert thrusters have the variable throat areas for the quick divert of the kill vehicle. The nozzle throat areas are throttled such that the mass flow is met for the required thrust for each thruster. Pintle valves are used for the throat area throttling purpose. The attitude control thrusters have the fixed throat area which will be used for the attitude control capability of kill vehicle. A pulsed motor has been designed to operate for divert thrust and attitude control for first few seconds and second motor (second pulse) will operate with a time delay after first motor operation. This is achieved by configuring an annular motor around the first rocket motor (which get emptied during the first pulse) and separated by two pulse separation diaphragms (PSD). The propellant gases flow into the first pulse motor and actuated by the first pulse rocket motor nozzles to produce variable divert and fixed attitude control thrust for second pulse duration.
Performance Evaluation of Rocket Motor End Dish Using Computed Tomography (CT)
Computed Tomography (CT) system with Linear Detector Array (LDA) generates a thin crosssectional image (slice) of an object where as with Flat Panel Detector (FPD) directly generates 3D volume from 2D X-ray projections. Further, CT images are free from overlying and underlying areas of the object and are highly sensitive to small density differences (<1%) between structures. This paper discusses about the efficacy of 3D CT for performance evaluation of Rocket motor End dish. The End dish experiences very high temperatures and very high pressures due to propellant combustion inside rocket motor, so the metal casing is bonded with composite liners to avoid its melting. A hole, which is drilled at an oblique angle through metal casing, later through liner should maintain single axis. Any skewness in hole axis and lack of bond integrity between multiple interfaces results in abnormal performance of rocket motor during its functional test. In such scenario, 3D CT technique was employed on End dish to find out the bond integrity, hole axis skewness and also to assess the performance of End dish after functional test. The salient features of 3D CT evaluation of End dish are highlighted.
Dynamic Analysis of Integrated Launch Package in the Barrel of Railgun
Electromagnetic launch technology was one of the important developing direction of new concept weapon. The projectile or armature could be accelerated to a high speed by instantaneous released electricity. Integrated launch package (ILP) was seemed as the main ammunition anti-armor currently. ILP could be endowed with stronger ability by using electromagnetic launch. In recent years, how to reduce or avoid gouging, grooving and transition in railgun barrel was the main research direction to increase lifetime of railgun. Most of these researches just discussed the effect between armature and rail. ILP as the final ammunition always contained three parts, armature, sabot and penetrator. The electromagnetic force mainly distributed on the armature. The movement of sabot and penetrator were contributed by the push of the armature. Dynamic analysis of ILP in the barrel was discussed in this paper to provide a reference to decrease damage in the barrel and increase the accuracy long rod.
Prediction of Real Gas and Non-Equilibrium Effects in the Gas Dynamics of Canister Launch Missile
There are many techniques have been developed to launch the missile from the canister. Two general categories of canister launched techniques are recognized, Self-Eject Launch (Hot Launch) and Gas Eject Launch (Cold Launch). Each specific technique has its own particular benefits and problems. One of the most reliable techniques for missile launch is Gas Eject technique in which hot gas generator is used to provide the force to drive the missile out of the canister. In this procedure, a solid propellant gas generator gas is ignited in the closed volume (Reservoir/breech) below the missile in the canister and resultant pressurization forces the missile out. In order to study and predict the variation of pressure, temperature and missile motion inside the canister during launch phase, gas dynamic model has been developed with many assumptions like Ideal gas, Constant Specific Heat, Jet impingement Heat loss, Turbulent model etc… In this present study we attempted to implement the presently available advanced techniques to improve the accuracy of launch dynamic predictions. Study has been done by implementing the effects of Real Gas (Variation of Compressibility factor (Z)) and Specific heat at constant pressure (Cp) variation with gas temperature during missile launch phase.
Effects of Sound Suppressors on Muzzle Velocity, Bullet Yaw and Drag
Little has been published regarding whether and how sound suppressors impact bullet flight, including velocity, bullet yaw, and drag. These parameters were compared for four different bullets fired from a .300 Winchester Magnum under four different muzzle conditions (no device and three different suppressors). While effects were not observed in all cases, results indicate that sound suppressors can have the effect of reducing bullet yaw and drag significantly, and can also have small effects on muzzle velocity. Results further suggest that bullets with a propensity to yaw demonstrate significant reductions in yaw and drag when shot through a two stage symmetric suppressor versus unsuppressed or with a conventional mouse-hole/K-baffle design.
Dynamic of Tubes Crossed by High Speed Projectiles, Influence of Tube and Weapon Geometry on Accuracy and Dispersion
Gun accuracy is influenced by several parameters during the in-bore projectile travel. The aim of this study is to determine the influence of gun barrel straightness on projectile exit conditions, in order to understand how to improve weapon accuracy. A tridimensional numerical model is created in order to vary this parameter and to study its influence on the ammunition behavior during internal ballistics. The model will be validated using experimental firings, particularly with accelerometers embedded in the ammunition. These firings have required the development of an optoelectronic system to transmit accelerations in real time. The good correlation of the experimental and numerical results proves the representativeness of the model. The model can then be used now to perform parametric analysis and to determine the most penalizing straightness shapes for gun accuracy.
Thermoelastic Analysis of Composite Railgun Housing Under Rapid Fire
Carbon fiber reinforced barrel can be applied to the lightweight design of railgun. The composite barrel will improve railgun performance with better flexibility and small muzzle disturbance. With magnetism-thermal-structure coupled analysis, this paper gives the transient thermal stress distribution of the composite barrel for single shot. Besides, two cases of a rapid fire with five shots per minute and ten shots per minute are studied respectively. In the end, dynamic strength of the composite barrel has been checked with specialized failure modes for both fiber wraps and metal rails. The results show that temperature rising of rails for single shot is higher with fiber laminate housing than with insulated steel plate housing. When the railgun undergoes a rapid fire, thermal stress of the composite housing and rails has an increasing tendency. The maximum rate of fire for the railgun must be limited to an acceptable level, considering that all materials of the composite barrel should remain linear elastic.
Dynamic Model of Rifle Bullets in Muzzle Flow
The development of high accuracy rifle has uncovered a need for understanding the movement of the bullet in muzzle flow. Recent researches have always been focused on computational fluid dynamics (CFD) and experimental research on the muzzle flow, which released many data, such as velocity and base pressure drop of projectile. Due to CFD tests are timeconsuming, a dynamic model for spatial motion of projectile is established. In this model an empirical relationship is utilized for the base pressure of projectile, and the model is assumed that the base pressure is along the axis of barrel which applied on the tail cone of the bullet; The spatial motion equations deduced from the mass center motion equations and Euler equations of motion are solved with Runge-Kutta method. A 7.62 caliber bullet is tested to verify the dynamic model. The result agrees with the CFD and experimental data, which shows that the model is applicable in predicting the translational motions, besides the angular motion of projectile is also presented, which can be the initial condition of exterior ballistics to analyses the firing accuracy.
Dispersion Sensitivity Analysis & Consistency Improvement of APFSDS
Medium Caliber Sabot for Efficient Use of Polymer Materials with Pressure Dependent Yield Strength
In kinetic energy projectiles, the buttress groove is conventionally used to transmit load between the long rod penetrator and the sabot during gun launch. The buttress groove geometry traditionally features a 7° driving flank angle but this angle can be varied to reduce the peak effective stress while increasing the peak hydrostatic or “pressureâ€ stress along the groove root. Through modeling and simulation, it is shown that the increased pressure stress can be advantageously employed in combination with a sabot material that exhibits pressure dependent yield strength to survive gun launch.
Separation of sabot petals is a critical procedure in intermediate ballistics affecting accuracy of the final hit of the penetrator of the fired ammunition round. Design of sabot petals has been an important concern supported by modeling and simulation studies of sabot separation. Computational fluid dynamics studies of the same have hitherto addressed feasibility of coupled fluid dynamics and 6 DOF simulations employing fixed sabot designs. The use of dynamical meshes for supersonic air flow is in its infancy as each simulation run for a given sabot geometry is highly computationally intensive. Good support can still be offered to sabot petal design by using analytical models, like the one by Reinecke and Guillot and its subsequent improvements. We present and study an improved model which better captures the role of the sabot petal scoop. In particular, we study how changes in the shape of the scoop affects the sabot separation kinematics. The sabot assembly assumed to be axisymmetric in shape and other major design parameters are kept the same when the scoop shape is changed.
A Novel Electromagnetic Launching Assisted Bore Ram Accelerator and its Potential Applications
A novel launching method, the EML assisted bore ram accelerator, is presented to launch the payload. It will accelerate the payload as fast as possible, while keeping the overload acceptable. First of all, the payload is launched by EML to achieve the speed of 800~1500m/s. Then, the ram accelerator increases the velocity of payload to a higher one, greater than 2000m/s. The proposed launching method can be implemented very flexibly, both vertical launching and oblique launching can be adopted. Moreover, it can be set up based on land-based, and ship-based. Here, we discuss on the solution which launching a 40kg payload to about 120km sub-orbit with the proposed method. This new launching mode can be used to study the space science, providing a reusable, affordable, safe and reliable method to exploit the terrestrial space.
Numerical Investigation on Influence of Precursor Flow on Combustion in Muzzle Flows
The muzzle flow with and without precursor flow is simulated. The AUSM+ (Advection Upstream Splitting Method) scheme is adopted to capture the shock waves in the muzzle flow. The combustion in the muzzle flow is considered using detailed reaction kinetics model. The model consists of 9 species and 12 reactions. Besides, an inert species is added to trace the precursor gas. By analyzing the motion of the inert gas, the interaction of the precursor gas and the propellant gas is obtained. By comparing the results of the muzzle flow, the influence of the precursor flow on the muzzle flow is discussed in detail. The present of the precursor flow makes the jet boundary more complex and increases the intensity of combustion.
Numerical Simulation of the Muzzle Flowfield of Embedded Aircraft Gun
The muzzle flow of aircraft gun is significantly influenced by the flight speed. Based on the Naiver-Stokes equation and k-epsilon model, the Roe Flux Differencing Scheme was used to simulate the muzzle flowfield of embedded aircraft gun in four different states, viz. inflow velocity of 0, 1.25, 1.5 and 2.5Ma. The structures of the muzzle flowfield were shown clearly, including the interaction process between the muzzle flow and supersonic inflow. The structure features were discussed in detail by comparing the parameters in the static and supersonic flight state. Furthermore, the influence of inflow velocity on the muzzle blast intensity was analyzed.
Influence of the Obturator Breakage on the Sabot Separation of an APFSDS Round
These works had for purpose to study how a dissymmetry in the obturator breakage during the sabot discard may affect the point of impact of a large caliber APFSDS round. For that we used a detailed 3D FEM model to simulate the behavior of different configurations of obturators, with configurations adapted to emphasized symmetrical and non-symmetrical behaviors. The results show that an influence on the Target Impact Dispersion may exist, which may vary from negligible to noticeable on the overall TID.
Investigation of the In-Bore Structural Integrity of a Kinetic Energy Projectile
In-bore failure of a large caliber tungsten heavy alloy long rod penetrator has been studied. A 2D axisymmetric finite element analysis has been carried out to check its in-bore structural integrity. The objective of structural analysis has been to obtain accurate stress field in the penetrator. Three phase approach was adopted to analyze the problem. The analysis involved quasi static analysis of the entire penetrator and fracture mechanics approach. A high stress concentration with steep spatial gradient has been found in the fillet region of rear thread/groove of the penetrator. Although, stresses are very high at the fillet of the rear groove, they reduce to safe limit rapidly. Though bulk failures are not predicted, high axial stresses at thread roots can cause catastrophic failure when cracks are present. Fracture mechanics based approach has been used to find the desired fracture toughness for a given crack size.
Intermediate Ballistics Modelling including Muzzle Brake
A method for intermediate ballistics modelling is presented. The method is used to study the effect of muzzle brakes with a passing projectile. Pressures, velocities and impulses are computed using a thermodynamic interior ballistics code (lumped parameter code) for projectile travel within the barrel. Then Computational Fluid Dynamics (CFD) simulations are used for gas and projectile travel outside the barrel. CFD simulations are performed both with and without a projectile and the results compared. Three generic muzzle brake geometries are used for simulations. Impulses computed from thermodynamic model and CFD model are combined to evaluate the gun recoil. The CFD model, with initial conditions transferred from the thermodynamic model, can further be used to analyse the influence from the muzzle break on the flow.
Euler Computations of the Direct Coupling between Interior, Intermediate and Exterior Ballistics of a Self-Propelled 155 mm/52-calibre Gun-Howitzer Installed on a Truck Chassis
The main objective of this work is to assess the pressure levels obtained over a new designed 155 mm/52-calibre gun-howitzer during a firing sequence. For this design, the barrel muzzle exit is really close to the truck driver’s cab. It is then essential to verify that the wall pressure levels resulting from an artillery firing are compatible with the considered material. For this purpose, the CFD ballistics code FREIN 3D is used to compute the direct coupling between interior, intermediate and exterior ballistics of this new 155 mm/52- calibre gun-howitzer. A simplified geometry is considered for the CFD computation and the computational domain involves only a part of the truck chassis since only the pressure levels over the first part of the truck are of interest. One case is considered, corresponding to an indirect firing.
Coupling Vibration Model of In-Bore Balloting
The objective of this work is to find the cause of high variability of jump. The presented model has a new feature that the total clearance gap between rod, sabot and tube is incorporated in the calculation. The clearances are found responsible for the shot-to-shot dispersion of impact together with the regional warp of tube center line. The balloting model based on vibration theory makes the degree of freedom drastically less, and made it possible to calculate the motion of one shot in 10 minutes. This allows us the parametric calculation of each candidate factor. The formulated model can predict the details of rod motion in a dynamically deflecting tube. We could not have pointed out the name of item that brings about high variability though, it has become possible to tell the critical values of the specific property that is responsible for high variability of jump.
The Characteristics of Man-Rifle Interaction in the Entire Process of Rifle Fire
The current researches on characteristics of man-rifle interaction focus on the shooting process after firing without considering the laying stage before firing and the restoring stage after firing. To further understand the characteristics of man-rifle interaction in the entire process of rifle laying and firing, this research comprehensively tests the entire process of standing firing without support. Also the research proposes a comprehensive test method of man-rifle interaction experiment based on 3D motion capture and plantar measurement. This research divides the entire process of rifle fire into three stages of laying, shooting and restoring in action sequence. The result shows that, during the laying stage before firing, the stability of shooter’s holding rifle is affected by the place of holding, the weight of rifle and so on, which is presented by slight shaking. Shooter’s control over rifle in the Y (horizontal) direction is obviously weaker than that in the X (shooting) and Z (vertical) direction. The stability during this stage has a great influence on the accuracy of first firing; During the firing stage, the period of 3-round burst is less than 300ms,so that human is in a passive and adaptive stage. Under the effect of impact among powder gas and firearms-related parts, phenomenons can be seen that: muzzle displacement, plantar pressure center displacement and speed all have a jump increasing along with the number of shooting, which is consistent with the previous researches; And then man-rifle system will back to the laying stage after a restoring stage of about 0.8 seconds under human’s own control, which is influenced by human’s self-adjusting ability. The restoring time is variable and it greatly affects the accuracy of shooting the objective again. This research provides theoretical reference and experimental basis for further revealing the mechanism of man-rifle interaction, optimizing the ergonomics design of rifle and promoting the competence of soldier training and actual combat.
Victim’s Posture and Protective Clothing Changes the Approach in an Edged-Weapon Attack
Diverse groups of people use edged-weapons (i.e., knives, spears, swords) professionally. The training received affects how the edged-weapon is used and the area of the body targeted. There is a growing body of information available on the internet which is aimed at the training individuals in offensive knife attacks. This poster aims to raise awareness of this issue and highlight how a trained individual modifies an attack sequence depending on their victim’s posture and the protective clothing worn. A male trained in the Filipino martial arts discipline of Eskrima performed attack techniques on a static mannequin covered with a long sleeved upper body garment and leggings, a police custodian helmet and a HG1 + KR1 police body armour. In some simulated attacks the target was also dressed in a police highvisibility tactical vest on top of the body armour. High-speed video was used to capture each simulated attack and the impact location on the torso recorded using ultra-violet sensitive liquid applied to the weapon. Target posture was modified by adjusting the arm position of the mannequin. In a second series of experiments a PermaGel™ male target torso was used so that penetrating damage could be assessed. Data collected identified the change of attack due to victim’s posture and vulnerability of the neck, underarm area and groin.
The Influence of Soil Temperature on Blast Intensity of Buried Explosive Charges
Soil conditions, just as soil type, particle dispersion, moisture content, degree of saturation and other parameters are influencing the intensity of a blast. None of the various existing standards present an unambiguous uniform definition of all above soil conditions for blast tests. Plasan R&D team investigates the soil parameters and their effects on blast intensity in order to produce, given a particular soil, its blast intensity with respect to reference standard utilized. Such efforts were previously presented in Ref. [1],[2],[3]. This prior research proved that the degree of soil saturation has a critical effect on the intensity of the blast. It demonstrated that soils of low density with a high degree of saturation produce a higher blast intensity than denser soils with lower saturation. Recently, in some experiments carried out at various field tests, the blast intensity and the damage observed in the tested article was more aggressive than that detected in preliminary experiments conducted at Plasan test site and predicted by the simulation. The key variance concerning those tests was weather conditions that influenced soil temperature. Those tests were conducted in wintertime. The environmental temperature was near or below freezing. Generally, no known standards specify temperature of the soil for mine blast test. There is little information in the literature about the influence of frozen soil on the blast intensity. As part of the effort to predict accurately buried mine intensity in different conditions which will include moisture and temperature effects, we conducted a series of small scale blast test, utilizing dedicated designed test apparatus, using soil temperatures between +4 to -16°C, at designated soil saturation levels. The results of these tests showed that frozen soil may double the blast intensity compare with the same soil, in terms of density and saturation, at temperature above 0°C.
Determination of the Iso-Damage Curve of Different Types of Components against Blast Wave
The strength of components against blast waves has been studied largely especially in the case of the nuclear blast. These works show that the damage is well defined by the pressure level and the recovery time of assemblies or sub-assemblies. In the frame of this work, we studied the effect of an explosive charge on different types of components. The reaction of an explosive charge in a ship breeds a propagating shock wave whose effects can induce severe damages on the different components set inside corridors and rooms. We seeked to determinate the damage level bred on different types of components by the detonation of an explosive charge inside a closed volume. Using the Johnson’s rule, we can establish the iso-damage curve for every type of components. The results show that the mass and the dimensions of the components have the main influence on the behavior of the component against the explosive loading.
Clear Ballistics Gel®: High Speed Retarding Force Analysis of Paraffin-Based Alternative to Gelatin-based Testing of Lead-Free Pistol Bullets
This paper presents high speed video analysis of 11 service caliber lead-free pistol bullets impacting Clear Ballistics Gel® with the dual purpose of assessing the equivalence of Clear Ballistics Gel® and calibrated 10% ballistic gelatin as test media and providing an initial assessment of wounding and incapacitation potential of these 11 service caliber loads. The present study suggests that Clear Ballistics Gel® results in lower retarding forces, erratic expansion, greater variations in penetration depth, and larger average penetration depths than calibrated 10% gelatin. Taken together with other results, testing in Clear Ballistics Gel® should only be used to identify candidates for further testing in calibrated 10% ballistic gelatin; it should not be used for the selection of duty ammunition without further performance testing in calibrated 10% ballistic gelatin. Depending on the wound profile and penetration desired for a given application, several loads analyzed here may warrant additional study. The Liberty Civil Defense 60 grain lead-free hollow point had the largest peak retarding force, temporary cavity, and permanent cavity while meeting the oft-cited minimum penetration requirement of30 cm.
Dynamic Mechanical Analysis of Fiber-Based Ballistic Protection Materials
The paper presents results of dynamic mechanical analysis (DMA) of fiber-based laminates produced for hard ballistic applications. The traditional testing of ballistic protection systems with the use of live ammunition requires a suitable firing range as well as additional measuring equipment. Due to significant costs of such testing development of a reliable and cost-effective method of determining mechanical properties is well justified. The tested hard ballistic laminates included two types of materials Dyneema® HB80 and Twaron CT 736. The experiments were carried out with the use of DMA Q800 analyzer produced by TA Instruments. The rectangular samples with dimensions of 60x10x2 mm were subjected to dual-cantilever bending with the heating rate of 2K/min at three frequencies of applied force measuring 1, 10 and 100 Hz. Values of dynamic storage modulus E’, dynamic loss modulus Eâ€ were presented in dependence on temperature in the ranges from -500C to +600C and +300C to 1500C. The influence of frequency of applied force on the results was also investigated for the polyethylene sample. The principle of operation of DMA analysis, measured values as well as proper experimental conditions are described. The experimental results obtained with DMA of polyethylene and aramid ballistic materials are evaluated and compared. The main aim of the research was to apply advanced testing technique for evaluation of ballistic protection materials in order to determine their mechanical properties.
Selected Issues of Lightweight Bulletproof Vests Design and Testing
The paper presents selected issues of lightweight bulletproof vest development with particular emphasis given to soft ballistic materials. Three types of Ultra High Molecular Weight Polyethylene (UHMWPE) were selected for ballistic resistance tests. They were Dyneema® soft ballistic materials SB21, SB51 and SB71. The main aim of the research was to determine the minimum number of layers of each material that meets the protection requirements of the Polish and NIJ standards, taking into account efficiency of the armour as well as the limit of back face signature (BFS). Key characteristics of fiber-based polyethylene materials as well as ammunition used are pointed out. The material sets consisted of layers set together loosely and secured on the sides with technical tape. The ballistic resistance tests were conducted in the ballistic tunnel at stable atmospheric conditions. The first stage of experiments involved testing the samples with the use of two types of pistol ammunition: 7.62x25 mm TT FMJS and 0.44â€ Remington Magnum SJHP and after determining the sufficient number of layers of each material the arranged sets were subjected to V50 tests with the use of fragment simulating projectiles (FSP). The second stage involved testing of polyethylene and aramid layers with two additional types of pistol ammunition with increased penetration capabilities that is 5.7x28 mm SS190 and 4.6x30 mm DM31.
The Effect of Clothing on Gunshot Wounds in Gelatine: The Naked Truth
There is a paucity of literature regarding the effect of clothing on gunshot wounding patterns. In this paper the effect of a military clothing layer compared to its absence on patterns of gunshot wounding was investigated using calibrated 10% gelatine and two types of military ammunition: 7.62x39mm and 5.45x39mm. In total 18 blocks of 10% gelatin were used, 12 shot by 7.62x39mm rounds (6 with a clothing layer and 6 without) and 6 shot by 5.45x39mm rounds (3 with a clothing layer and 3 without). Multi-Terrain Pattern (MTP) issued military uniform was used to provide the clothing layer. Samples were analysed with high speed video and dissection, and compared using appropriate statistical techniques. Results showed no significant effect of a MTP clothing layer on wounding patterns in gelatine blocks with either ammunition type when compared with unclothed gelatine blocks.
The Protective Performance of Selected UK Police Body Armor Challenged by m75 Grenades
UK Police ‘soft’ body armor is designed to provide protection from sharp-weapons and low-velocity pistol ammunition; if ‘hard’ armor plates are fitted then high-velocity rifle protection is provided. Several different levels of protection for both soft and hard armor are available and these are tailored to the individual police officers’ role. The level of protection offered by these types of armor from fragmentation threats is not known as fragmentation is not typically considered a threat to UK Police Officers. However, fragmentation from devices such as grenades may be a threat to certain specialized units and during terrorist incidents. In this work, neither the soft nor hard UK Police body armor (HG2 and RF1 respectively) investigated were perforated when challenged by M75 Yugoslavian grenades at a distance of 1 m from the point of detonation. The effect due to blast was not considered. The work has provided confidence regarding the performance of selected police body armor against fragmentation from a selected grenade threat.
An Investigation into the Blast Effects on Civilian Personnel Protective Armour
With the ever increasing threat of terrorist attacks, understanding the blast effects on the human body is becoming increasingly important. Typically terrorism based events often occur around non-military, high profile, large population areas to achieve the greatest number of causalities. As such, the blast loading effects produced from such event are not limited to military personnel, but also civilians. One area that is often overlooked is the blast effects on law enforcement personnel wearing body armour. This work explores the influence and loading profiles that the typical police body armour has upon the blast loading experienced by the wearer.
The Influence of Wind on Gunshot Localization Accuracy
In this study the importance of wind for acoustic gunshot localization, i.e. its influence on the accuracy of the direction of arrival, is studied. A correction factor is applied to account for the influence of wind on sound propagation. The final objective of this work is to locate marksmen using acoustic vector sensors (AVS) instead of arrays of conventional microphones. To allow for comparison with these AVS, experiments were performed, in which the direction of the sound source was evaluated using two microphones. By estimating the time difference of arrival and by cross-correlating both channels, it is possible to compute the source direction. The direction of arrival estimation was accurate to 1.9 degrees at wind speeds below 2 m/s. These measurements can serve as a baseline for accuracy tests with AVS.
A New Model for Experimental Modeling of High-Explosive Warheads
This document deals with the experimental modeling of high-explosive warheads. This type of modeling is very common in weapons programs because it is implemented as soon as it is necessary to study the effects of explosive devices. These models are used in lethality and vulnerability codes to assess weapon performance and the vulnerability of combat systems. This publication is about creating a new model which, unlike the classic Z-data model [1] contains the characteristics of each fragment. We will refer about it as the FLE model ("Fichier Liste d’Eclats" in French) and present it through this document, as well as the potential gains related to its use through examples treated with the two types of modeling.
Study on the Adaptability of Insensitive Explosives in Shaped Charge
In order to improve the insensitivity of the shaped charge warhead, the adaptability of the NTO-based explosive and the TKX-50-based explosive in the shaped charge warhead was studied in this paper. Insensitive explosive formulations were selected by analyzing the density, pressure and detonation velocity of the existing insensitive explosives. In order to obtain the plan of vice grain, the detonation and detonation propagation characteristics of the selected insensitive explosive formulations were studied. DOP experiments were conducted to compare the armor-piercing capability of the shaped charge warhead using insensitive explosives with and JO-8 explosives respectively. Results show that all the static armor-piercing capability of shaped charge warheads, which applied NTO/CL-20, TKX-50 and TKX-50/RDX respectively, is more than 7 times of the charge diameter. This can meet the application requirements efficiently. Among these warheads, the compatibility of NTO/CL-20 blended explosives with the shaped charge structure is better, and the vertical static armor-piercing capability of the corresponding warhead is 8%~10% higher than that using JO-8 explosives meanwhile the static armor-piercing capability is greater than 9 times of the charge diameter.
Projection Criteria for Insensitive Munitions and Hazard Classification
The origin of projection criteria for Insensitive Munitions (AOP-39) and Hazard Classification (UN Orange Book) was investigated. Current distance-mass relations were reproduced with TRAJCAN trajectory analysis by using launch energies of 8, 20 and 79J and calculating the maximum impact distance reached by a natural steel fragment launched from 1 m height. The results show how distances would vary with assumed fragment shape and material. It was also observed that at the maximum throw distances, the impact energy is generally much smaller than the launch energy. This led to the development of new distance-mass relations that are based on the aforementioned energy criteria at 15 m impact and beyond, rather than on launch energy.
Assessment of Rate Dysfunction of Statistical Armour Against RPG-7 Family Threat
The RPG-7 infantry rocket constitutes a significant threat for the vehicle protection’s design. The evaluation of statistical armour, integrated on vehicles to defeat these rockets, is long and complex. The challenge is to explore all configurations of impact with the minimum of test. This paper proposes an experimental approach to estimate the protection probability offer by a kind of statistical systems. The methodology is based on the shortcircuit observation during grenade/protection interaction with specific instrumented trials and an associated statistical processing. It allows getting details on physical phenomenon leading to dysfunction and also estimating its occurrence.
Research on Ground Target Recognition Algorithm Based on Multiple Column Array Laser Radar
In order to improve the identification probability of the parachute terminal sensitive projectile in complex battlefield environment, which can recognize armor targets from camouflaged targets and conventional vehicle targets with high probability, and to meet high real-time requirements of algorithm in the terminal sensitive projectile detection system, the method based on Multiple linear array Laser Radar is proposed to achieve 3D Ground Object Automatic Target Recognition. Firstly the OTSU algorithm bounded by 3-D point cloud was used to obtain the height binary image and then morphology filter processing was performed on the binary image from the previous step to get the suspected target. Finally, the target was identified based on the target height features and the enclosing rectangle features. The results of the simulation of the target model show that the proposed method can realize the accurate ground target extraction.
Controlling the Fragment Dispersion for a Fragmentation Warhead and its Effect on Lethality
Effectiveness of a fragmentation warhead is generally related to the fragmentation characteristics such as the number, mass and velocity of the fragments. Distribution is also an important but mostly ignored feature of the fragmentation. Especially, in most of the lethality or vulnerability calculations, fragmentation of a warhead is assumed to have a homogeneous distribution. In other words, the assumption says that the fragments dispersion occurs such that fragments are uniformly or randomly distributed in a solid angle. However, this assumption does not work effectively in all conditions. Particularly, for some controlled fragmentation warheads used against relatively small targets, discrete dispersion of the fragments should be considered during effectiveness calculations. In this study, it is aimed to show that a homogeneous fragmentation distribution should be obtained as much as possible when using pre-shaped fragments for higher effectiveness. Also, the significance of homogeneity in fragment distribution in addition to the mass and number of fragments is presented with the methodology, analyses and comparisons.
Investigating Potential Solutions to Increase the Ballistic Protection of Structural Weak Areas in Armored Vehicles/KADDB Experience
Evaluating the protection level of armored materials used in vehicles is NOT sufficient in ensuring that the vehicle provides full protection against assigned threats. This is due to the fact that the design of any vehicle includes joints, overlaps, welds, bolts, etc.… that was proven buy extensive experiments to have significantly less protection capabilities compared to the main structure of the vehicle. This study focused on the Heat affected zones HAZ is particular associated with welding armored plates. In welded armored plates, the extensive heat creates an area referred to as the "Heat Affected Zones HAZ" that has significantly less ballistic protection capabilities due to the change in their microstructure, the size of the grains and their distribution and many other factors. The aim of this work was to investigate the effectivity of potential solutions implemented to overcome the reduction in the ballistic protection of the Structural Weak Areas (SWAs) from a test and evaluation point of view. Solutions investigated in this study included; Increasing the thickness of the base material reducing the heat affected zone’s size and severity, replacing the conventional welding techniques with sand blasting, gluing and ballistic coating and finally special Multi-layer overlapping techniques as a solution most suitable in Corner Joint welds. All three potential solutions have showed success in resisting the assigned threat but each with its limitations such as; increased effort, cost and weight which determine the selection of one solution technique over the other.
Behind Armor Blunt Trauma: Recreation of Field Cases for the Assessment of Backface Signature Testing
A total of 47 real-world cases were re-created in a laboratory environment. Cases were identified from the IACP/Dupont® and Safariland survivors’ databases. Exemplar armor was obtained for testing in the laboratory. Details surrounding the incident were determined and the ammunition and stand off distance were matched. The armor was placed on the standard preconditioned roma plastilina clay block and struck in the same location as reported in the case study. Both depth of deformation and volume of crater were recorded. Based on the analysis, the average depth of deformation for those cases involving minimal soft tissue damage (i.e., bruising) was 29.2 ± 12.4 mm. The average depth of deformation for those cases involving more severe injuries was statistically greater at 43.6 ± 27.3 mm (p<0.05). The data indicate a 50% risk of severe injury with a deformation of 43.6 mm. (95% CI [33.9 mm, 5.3 m]).
Assessment of the Possibility to Use X-Ray Diagnostic Systems— Electron Linear Accelerator and the MU17F 225-9 System in Non-Destructive Ammunition Tests of Ammunition
The paper presents the results of comparative tests of two x-ray systems used for non-destructive testing of ammunition - Electron Linear Accelerator and MU17F 225-9 system. Described diagnostic kits come from different manufacturers, one is a German company YXLON - MU17F 225-9 and the second set is of Polish production and was developed at the National Center for Nuclear Research (NCBJ). The study describes each X-ray system in terms of their technical parameters. Then different types of ammunition selected for testing, having: different thickness of the body walls, diverse fill of the projectile and the complexity of the structure. Then, tests of each kind of ammunition were performed using two systems. The received X-ray images were subjected to image processing and analyses were carried out for an evaluation of the each system suitability for ammunition diagnostic testing.
Comparing the Backface Deformation Behavior between Soft and Hard Body Armors
Hard and soft body armor employ different mechanisms for defeating the incoming threat; however test standards for evaluating both types of body armor systems use the same metric with regards to backface deformation (BFD). To understand the limitations of using the same metric for BFD, it is important to understand the backface signatures for both types, and where the signatures overlap and differ. Using a thoracic rig designed to measure the dynamic behavior of the BFD, the depth, strain rate, velocity, and diameter of deformation were examined behind hard and soft armors. Generally, the hard armor had greater depths and rates of deformation than the soft armor systems. Ballistic conditions that resulted in similar BFD behaviors in the hard and soft armors were identified. By identifying conditions that result in similar deformation behaviors, further research can be performed to determine if these conditions result in similar injuries.
The Effects of Composite Sandwich Plate on Explosive Charge by Fragment Impact
This paper presents the numerical simulation of the response of composite sandwich plate on explosive charge by fragment impact, representing that composite sandwich plate structure has good capability of explosion resistance. The theory studies show that the composite sandwich plate structure with “hard-soft-hardâ€ can effectively reduce the internal pressure of the explosive and improve the capacity of explosion resistance from the fragment impact. The results of simplified numerical models, carried out using Ansys/AutoDYN, are validated with experiments. Two single-layer metal plates and four composite sandwich plate structures are chosen as the barrier of cylindrical explosive charge Comp-B. The internal peak pressure of explosive and the transmission coefficient of shock wave under the impact of tungsten alloy fragment at 1710m/s velocity were investigated. The critical initiation velocities of fragments for explosive with different barriers were obtained. The simulation results indicate that the composite sandwich plate structures have smaller transmission coefficients and smaller internal pressure of explosive than single-layer metal plates. The predictions provide an insight into the vulnerability and security of warhead.
Effect of Blast Mitigation from Multiple Fluid Containers
A series of experiments were conducted to investigate the protection provided by multiple water-filled containers in a range of geometric configurations, by assessing the deformation of a steel target plate. The configurations evaluated varied the number of containers as well as the gap widths between the containers, and included a comparison to an equivalent areal density of steel. In addition, the effect of placing the charge between two containers was assessed. The study found the water-filled containers out-performed their steel counterparts for all cases. As the number of water-filled containers increased, the overall deformation of the target plate was reduced, with the highest mass efficiency achieved by the case with the most water coverage. Introducing gaps between the containers reduced their blast protection capability, especially when the charge is placed in-between the containers. However, there was no arrangement of water-filled containers in this series of experiments that did not provide some level of blast mitigation. It was observed that the blast mitigating mechanisms specific to a water-filled container were enhanced as the amount of water was increased.
A Methodology for Structural and Component Damage Assessment of Building Targets
One of targets of increasing significance in recent operations is building. The Joint Munitions Effectiveness Manual (JMEM) approaches for evaluating structural damage to buildings use the Building Mean Area of Effectiveness MAEBLDG (in square meters in the ground plane) as the Effectiveness Index (EI). MAEBLDG, the numerical values are classified, is used to describe the damage function for building and is area over which a weapon will damage the building. With this MAEBLDG values, the building damage is estimated for specific the building dimensions and weapon delivery accuracy [1]. In general the warhead detonates external to the building in air or after penetrating the roof, walls and floor slabs. It is inadequate to use the fixed MAEBLDG values for the specific building types since the MAEBLDG varies as the detonation location at the building target. Target elements inside buildings are usually personnel or equipment. In many cases, it is only required to kill the function or activity performed inside the building rather than destroy the building itself. Therefore the damage should be considered in two ways:1) structural damage and 2) functional damage. This paper deals with the methodologies to estimate both structural damages of buildings caused by detonations insides or outside the structures without using MAEBLDG concept. This method uses the specific weapon-structure interactions and Monte Carlo to capture the delivery accuracy of the weapon.
Study on the Influence of Temperature Rise in Penetration of Anti-Ship Warhead on Charge Stability
Based on the thermo-solid coupling algorithm of LS-DYNA, a calculation model of the penetration control of a semi-armor warhead is established. The numerical simulation of the semi-armor-piercing warhead penetrates the 16mm thick 945 steel plate with the speed of 0.8Ma-2.6Ma The temperature distribution of the shell and the temperature of the shell and the charge were obtained by considering the effect of plastic work heat transfer and friction heat on the shell and charge temperature. The numerical simulation and theoretical analysis show that the maximum temperature of the shell and the charge increases with the increase of the penetration velocity, and the maximum temperature of the shell surface is lower than the phase transition temperature of the shell material at the penetration speed of 0.8Ma. When the penetration speed is 2.6Ma, the maximum temperature inside the charge is lower than the critical hot spot temperature of the main charge explosion, which will not cause the main charge to be exploded, which has little effect on the stability of the charge during the penetration process. The numerical simulation results are in good agreement with the experimental results.
Research on Sectional Type Horizontal Cutting Interception Warhead
Sectional Type Horizontal Cutting Interception Munitions is a new warhead which can damage effectively, destroy and detonate the coming missile. Based on LS-DYNA software, LEFP formation, Flight Characteristics and penetrating process of the Sectional Type Horizontal Cutting Interception Munitions were simulated based on different detonation mode. The numerical simulation results show that the designed Sectional Type Horizontal Cutting Interception Munitions can form linear EFP with more than 2,200 meters per second velocity and can penetrate the 45# steel target with 20 millimeter thickness and the ability to initiation. The munitions provide references for design of Horizontal Cutting Interception Munitions of air defense anti-missile rocket.
Effect of an Explosive Charge with a Shell Close to a Metallic Plate
The reaction of an explosive charge close to a structural metallic plate is a strong threat for a ship. This situation is able to occur during the handling of the ammunition inside and can lead to the plate tear. The problem of the interaction of a naked explosive charge in contact with a metallic plate has been studied previously. In the following work, we elaborate an analytical model in the goal to quantify the induced effects by the detonation of an explosive charge with a shell on a metallic plate. In this way, we used the same main hypothesis than developed in the previous study.
Determination of the JWL Coefficients of the Hexomax Explosive
The replacement of plastrite by Hexomax leads to determinate and validate the equation of state parameters of the detonation products, in the goal to make performances numerical calculations of this energetic material. The Chapman- Jouguet state is calculated using two ways, firstly from simulations with the thermo-chemical code named SIAME developed by the CEA for the French DGA and conventional defense applications, secondly from an approach based on empirical relations available in the literature. The hypothesis of a mean value for the polytropic coefficient in the ambient state of detonation products and also for exponential decreasing members coefficients of JWL equation allows to reach to other parameters according the strength to respect the detonation CJ state. Inside SIAME, these coefficients are obtained by minimization of the JWL equation isentropic form of the detonation products CJ expansion. Used in a hydrodynamical calculation code (OURANOS, LS-DYNA), JWL parameters allow to compare the numerical simulation results to experimental results of the cylinder test. The correlation is very good with parameters from the thermo-chemical simulation. The empirical method looks like a FREM (« Fast Running Engineer Model ») leading to a good approximative solution of JWL parameters when the necessary enthalpy of formation for the thermo-chemical simulation is not available. The JWL parameters are used afterwards to evaluate the Hexomax blast effects for aerial detonation.
Numerical Simulation and Experimental Investigation of Two Types of Shaped Charge Comprised of Reactive Material Liner
Two types of shaped charge comprised of reactive material liner, which can generate exothermal reaction by certain external action, were designed to promote the damage effect. One design contained two layers of liners, which can form a short and wide explosive formed penetrator (EFP). The other design contained three layers of liners, which can form a long and thin EFP. The composition of reactive material is aluminum/polytetrafluoroethylene mixtures. The results of the numerical simulation and the experiments show that, the reactive material shaped charge with three layers of liners has higher penetrating ability on steel target, higher adaptive capacity on the burst height, higher cladding effect on the reactive material.
Effects of Multi-Point Initiation Control Parameters on Mach Wave Overpressure
Effects of the multi-point initiation control parameters (i.e., the initiation diameter and number of initiation points) on Mach wave overpressure are investigated. The interaction of a double symmetric detonation wave caused by two-point initiation is analyzed employing the Whitham method, thus obtaining the trace of triple point, the pressure and the area of the Mach wave acting on metallic liner at different initiation diameters. The pressure of Mach wave at different initiation points and initiation diameters was calculated. It is noted that the area of the Mach wave decreases but the pressure of the Mach wave increases as the initiation diameter increases. The pressure of central ultrahigh-pressure area at the vertex increases as the number of initiation points increases, but to be a constant when the initiation point number increases to a certain amount.
Influences of the Embedded Structure on the EFP Formation in the Compact Terminal Sensitive Projectile
To improve the damage efficiency of the compact terminal sensitive projectile with EFP warhead, it is vital to understand how the embedded structure (ES) affects the EFP forming performance. In this paper, the corresponding numerical investigation is focused on, where the fluid-structure interaction (FSI) method is applied and the experimental verification is employed. Based on the obtained quantitative relations between the formation performance and α (the ratio of the height to the maximum radius of the ES), the optimal design is further provided. The results indicate that: at a fixed volume, when the embedded structural length and width range 0.1-0.3D and 0.1-0.2D respectively (D: diameter of the EFP warhead) EFP forming velocity nearly keeps as a constant, 1760m/s; the height of ES can affect the detonation wave propagating range dramatically resulting in significant influences on the EFP aerodynamic shape and length-diameter ratio; under the given constraints, the EFP length-diameter ratio can reach the optimal value, 2.76 at height of ES 0.22D.
Study of Bonded Flake Structure in Explosively Formed Projectile with Fins
Numerical simulation of obtaining EFP with fins by a flake structure which was bonded to the internal surface of liner was carried out with the ALE method using LS-DYNA. An EFP with fins was obtained when the charge was detonated at the center point. The mechanism of forming EFP with fins was discussed based on curves of velocity of the liner. The result shows that such a charge structure can form EFP with four fins, the length-diameter ratio of EFP with fins is 2.41 times that of EFP and its velocity slightly below the velocity of EFP.
Quantification of Mechanisms for Blast Mitigation with Water-Filled Containers
Validated numerical simulations were used to investigate the physical mechanisms responsible for the blast mitigation provided to steel plates by water-filled containers in the near-field. The flying ring technique was used to define the spatial distribution of loading on the target, in order to isolate and quantify the importance of each mechanism. Increasing the height of the water-filled container was found to increase the loading at the top surface of the container. To offset this additional loading, the roles of the shadowing, mass and spreading mitigation mechanisms were enhanced as the height of the container increased. This resulted in the taller containers providing superior blast mitigation. The trade-offs between the loading and mitigation mechanisms were shown to result in an optimized container radius.
Accuracy of Empirical Gurney Velocity Prediction Models
Gurney Velocity of an explosive is a required input into the standard Gurney Model of fragment velocity prediction from a metal cased explosive. It is a critical parameter in the comparison of compositions for performance prediction. Eight empirical Gurney theories discussed in this paper enable prediction of the Gurney Velocity of explosive compositions using differing Detonation parameters. Some parameters are easy to access, whilst others can be difficult to obtain. Only empirical methods are assessed here, being both simple to implement, but also giving reasonable accuracy. Aluminised explosive compositions are treated in an identical manner. Two Gurney Velocities exist for each explosive, ‘prompt’ for rapid case fracture and ‘terminal’ for ductile case expansion. This paper considers only the ‘terminal’ value, being the most important. Analysis of the accuracy of each empirical method is given and statistical comparisons made. Surprisingly some complex methods do not necessarily give any more accurate predictions.
Numerical Simulation on Forming of Triple-Layer Tandem EFP
The multi-layer tandem EFP warhead is one of the new concept warheads in the context of attacking new armor, such as composite armor, explosive reactive armor and soon. In this paper, a triple-layer sub-caliber hemispherical liner warhead is designed, and the forming process is studied by using ANSYS / LS-DYNA simulation software. Taking the velocity of the EFP and the length to diameter ratio as the performance indexes, the effect law of penetrator formation with structural parameters of curvature radius, the thickness of hemispherical liner and the height of shaped charge are analyzed, which provides a reference for the multi-layer EFP warhead. The results show that the effects of the various shaped charge structural parameters on the formation of independent EFP are different. Among them, the radius of curvature mainly affects the shape of each EFP; The bigger of the thickness of each layer liner, the faster of each layer liner separate; The influence of charge height on the EFP velocity and the length-diameter ratio of each layer is similar to that of the single layer liner, and the EFP velocity can be increased by increasing the charge height.
Study on Penetration Performance and Distribution Characters of Multi-Explosively Formed Projectiles
The aim of the investigations was to improve the penetration performance and distribution homogeneity of MEFP. Using 3D coupled hydrocode of Ls-dyna, influence of the material and geometric shape of the charge cover on the configuration and velocity of explosively formed projectile (EFP) were analyzed. Also, the influence of bracket’ geometric shape and the arrangement patterns of the charge covers on the distribution characters of MEFP were also studied. On these bases, three different kind of integral multiple explosively formed warheads were proposed and the penetration performance and distribution characters of MEFP were verified by experiments. The results show that: When inner and outer vertex angle of the arc plane charge cover is 130° and 135°, the EFP changes to the long rod type with the length to diameter ratio about 16. The cabochon bracket is helpful for obtaining good EFP configuration and improving the scattering angle and distribution homogeneity of MEFP. The equidistant array pattern is superior to the circular array pattern to obtain the better distribution homogeneity of MEFP.
Effectiveness of PG-7 Grenade after Passing through the Net-Armor-Numerical Analysis
Numerical analyses have been performed to investigate how the PG-7M grenade interaction with the net-armor affect the shaped charge jet formation and penetration capability. Two types of three-dimensional computer simulations were carried out. The first one include mechanical interaction between the grenade and two commonly used types of net armors. The deformation rate of the warhead and occurrence of the short circuit in a fuse of penetrating grenade were estimated. The second type of analyses included the phenomena of shaped charge jet formation and penetration into RHA plate. Since the simulations were carried out for both the deformed and undeformed warheads, it was possible to evaluate the influence of the grenade deformations on the shape charge jet penetration performance.
Study on Interference of Explosive Reaction Armor to EFPS with Different Calibers
Previous studies have shown that "sandwich" explosive reaction armor (ERA) has a large interference effect on definite EFPs. However, it is unclear whether the conclusion is applicable to different calibers EFP warheads. To investigate this issue, the processes of copper EFPs formed by various charge diameters warheads penetrating into 1/1/1mm ERA were simulated by AUTODYN-3D software. The shape, deflection angle, velocity, and residual depth of penetration of EFPs after passing through ERA were obtained. The results showed that the interference degree of EFP was nonlinearly decreasing with the increase of charge diameter. Its causes were analyzed from the perspective of interaction time. In order to verify the correctness of the numerical simulation, the pulsed X-ray photographs of the interaction between ERA and EFPs formed by 56mm shaped charges were obtained and DOP was measured. It turned out that the numerical simulation results agreed well with the experimental.
Study on Shock Initiation of Cylindrical-Shell Charge Impacted by Spherical Fragment
The numerical simulation of the interaction between spherical tungsten fragments and cylindrical Comp-B explosive covered by steel casing was carried out by using AUTODYN-3D software. The influences of the fragment impact angle θ and cylindrical charge curvature radius r on the impact initiation characteristics of the explosive are analyzed, and the critical initiation velocity of cylindrical-shell charge (CSC) is obtained. The results show that the impact initiation mechanism of CSC coincides with that of planar-shell charge (PSC). For CSC, the critical initiation velocity increases exponentially with the increase of the sine value of θ and increases nonlinearly with the increase of r, which indicates that the CSC is easier to detonate. In addition, another high-precision simulation software SPEED was used to carry out the initiation process of the insensitive explosive PBXN-109 under the impact of fragments, hoping to provide a reference for further study of impact initiation in reality.
Study on Penetration of High-Polymer Shaped Charge Jets
This study investigates the characteristics of shaped charge jet formations with a high-polymer liner, as well as its penetration capabilities, by experimental and numerical methods. Two types of liner materials were studied: a high-polymer PTFE liner and a pure copper liner. Pulse x-ray photographic technology was employed to observe the distent jet of the PTFE liner and the particulate jet of the copper liner. The simulation and jet radiography results show that the two jet behaviors with particulate and radial dispersion are ductile behaviors, and the two jet behaviors appear to be related to the liner material. The distent jet formation result from the liner material was crushed at the high-pressure region because the sudden pressure increase produces radial velocity, which results in lateral expansion. Compared with the typical copper penetration performance, the polymer distent jet had a larger aperture and lower penetration depth. Clearly, because of the low polymer liner density, this device will have limited penetration compared to that of a copper liner. The simulated results strongly agree with the experimental results.
Determination of JWL Equation of State Parameters of Explosives Using Cylinder Expansion Test
Several types of equations are used for modeling the relationship among the state parameters of explosives and computer implementation is mostly needed for predicting the behavior of explosives. During modeling of detonation characteristics of explosives in simulations, Jones-Wilkins-Lee (JWL) equation of state (EOS) is widely used. The parameters of JWL EOS are not always available for newly developed explosive compositions. In this study, cylinder expansion test has been utilized to determine parameters. Cylinder expansion tests have been performed for different Polymer Bonded Explosives (PBX) and TNT with the designed setup and JWL EOS parameters are obtained. Gurney constants are also derived by post-processing the test results. Pressure - specific volume ratio curves for these explosives are compared with the curves available in literature and seen that the results are close for similar compositions. Parameters are also verified with the comparison of open area blast measurement results with numerical simulation.
Flight and Penetration Characteristics of Explosively Formed Penetrators
Explosively formed penetrators are generally designed to penetrate a target and launched from long distance. Because aerodynamic characteristics of the penetrator affect its penetration ability, research on the flight characteristics is needed. Therefore, in this study, we predict flight characteristics and penetration ability of EFPs using the test and FEM codes. Flight tests were conducted to obtain the behavior of penetrator and these data were used to estimate penetration ability and aerodynamic characteristics. We expect that our results can be used to predict the characteristics of penetrator and to determine optimized EFPs
Experimental Research on the Influence of the Equivalence Ratio and Operating Frequency on the APDE
When the air-breathing pulse detonation engine (APDE) is with the central cone-scales valve(CCSV), the effect of equivalent ratios and operating frequencies has been studied, under the working condition of the gasoline as the fuel and the oxygen content coefficient of 5%. The experimental results shows that with the equivalent ratio increased from 0.97 to 1.26, the detonation wave’s peak pressure, the propagation velocity and the ignition time will increase, but the effective thrust will increase first and then decrease. Moreover, when the operating frequency is increased from 8 to 18 Hz, the ignition time will decreases, and however, the effect thrust will almost linearly increase with the operating frequency, and the average thrust of a single waveform is almost equivalent to 5.2ã€œ5.5N.
Laboratory Setback Activator Tests for Gun Launch Explosive Suitability
There is currently no agreed standard methodology for assessing the suitability of explosives for gun launch or for the determination of acceptance criteria for explosive fill defects. Laboratory setback activator testing has been used as an assessment tool for investigating the suitability of explosives for gun launch. Unfortunately, laboratory setback activator testing is not standardized and large variations exist in activator design, function and results between different laboratories. However, it is the only currently available tool for assessing an explosives safety and suitability to launch-induced setback forces. In laboratory setback activator tests, ignitions are observed at setback loadings that are much higher than produced in actual gun launched projectiles. This may be related to the defects in actual projectiles, which appear to be very different than the laboratory tests.
Three-Dimensional Numerical Research on the External Flow Field of Three-Tube Pulse Detonation Engines
To investigate the characteristics of external flow field of multiple-tube Pulse Detonation Engine(PDE), the physical model of a three-tube pulse detonation engine was established. The three detonation tubes fueled by H2/Air are put side by side and they are ignited at the same time. The three-dimensional space-time conservation element and solution element method (CE/SE method) was used to solve the governing equations. The corresponding three-dimensional non-viscous numerical calculation programs were made and the characteristics of the external flow field of three-tube PDE were attained. The propagation process of various wave systems in the external flow field of PDE was analyzed. The numerical results indicate that there is a negative pressure zone in the external flow field. A strong discontinuity surface appears behind the negative pressure zone, through which the negative pressure quickly increased to high pressure. The circular shock, arc-shaped shock and the expansion wave interact with each other and continue to replace and expand with the passage of time. The region where the shock waves were located has a higher temperature than the other region, and the temperature extremes appear on the shock wave front. The interaction between the wave systems and its effect on the operation process of PDE are analyzed, which can provide guidance for the structure design and experimental research of multiple-tube PDE.
Effect of Initiation Configuration on Blast Performance of Cylindrical Explosive Charge—An Experimental Investigation
Experiments were conducted on cylindrical explosive charge with three different initiation configurations viz., geometric center initiation, single line side initiation and two line side initiation. Blast pressure parameters were measured at different distances from explosive charge. Peak over pressure from single line initiated explosive charges along azimuth direction at 180o is about 40% more than that of point initiated charges at a distance of 1m from point of burst. Over pressure and impulse values of line initiated charges drop down to those values obtained from point initiated charges beyond a distance of 10 times charge diameter from point of burst. Total impulse is observed to be less in case of two-line initiated charge as compared to point initiated and single line initiated charge.
Investigation on the Formation Mechanism of Natural Fragments of Improvised Explosive Device
To study the key technical issues involved in the field of reconstruction of improvised explosive devices (IEDs), the formation mechanism of natural fragmentation under blast loading was investigated using the finite element code AUTODYN 3D with Mott’s stochastic failure model. The analysis of structural response, critical failure condition, as well as dispersion characteristics including initial angle and velocity of fragments were also carried out. Meanwhile, the effects of charge mass and structure were discussed. The results of the mass and number of fragments, as well as the radius of flight can be used to reconstruct the explosion scene of IEDs.
Measurement of the Spatial Specific Impulse Distribution Due to Buried High Explosive Charge Detonation
Buried high explosive (HE) charges represent a high threat to military vehicles. A detailed understanding of the physical processes involved in the loading of vehicle structures is necessary for an optimization of effective countermeasures and protection systems. In the following, a new test setup is presented that allows the experimental determination of the specific impulse distribution. It is based on a ring arrangement where the elements are nested into each other and the velocity of each ring is correlated with the local specific impulse at its position. The presented technology is applied to quantify the influence of the embedding material (alluvial sand, quartz sand), the burial depth and the water content on the local specific impulse distribution. The obtained data can be used as initial condition for the numerical simulation of occupant safety assessment and as input for empirical modeling of momentum transfer on structures.
Comparison of 3D Simulations with Data for the Interaction of an Array of Linear Shaped Charges Against a Complex Target Configuration
Shell International Exploration and Production Inc. is developing an Emergency Severance Tool (EST) capable of severing various types of marine riser systems used in deep sea underwater drilling operations. The purpose of the tool is to rapidly release the surface drilling rig from the blowout preventer located on the seabed in the event of a blowout scenario, as occurred in the Macondo Gulf of Mexico event. The present design incorporates an array of linear shaped charges which surround the marine riser and are designed to sever the marine riser and the enclosed steel drill string. On May 14th, 2015, Lawrence Livermore National Laboratory (LLNL) performed an experiment designed to study the penetration of an array of shaped charge jets through an intact drill collar. These data are used to validate and calibrate numerical models of the shaped charge jet performance. Results from these experiments show that the performance and penetration was accurately predicted by simulations using LLNL’s ALE3D code.
Characterization of a Linear Shaped Charge with Increased Standoff Capability
In response to the blowout scenario in the Gulf of Mexico event in 2010 and the loss of lives and equipment, Shell International Exploration and Production Inc. started work on designing an Emergency Severance Tool (EST) to rapidly sever the marine riser assembly that connects the drilling rig on the surface with the blowout preventer on the seabed. LLNL proposed a concentric array of linear shaped charges to sever a 9.5â€ diameter by 3.25â€ wall steel drill collar located inside a 18.75â€ diameter marine riser assembly. The charges had to penetrate a thin layer of steel and up to 240mm of drilling mud (density ~ 2g/cc) prior to severing the drill collar. A linear shaped charge was designed based on ALE3D simulations, with the objective of maintaining severance capability at a standoff of up to 16â€. This initial simulation-based design was tested in two characterization experiments which compared jet behavior in air with jet behavior in drilling mud. Both tests were fully instrumented to measure charge performance, jet speed, shape, and penetration for comparison with preshot simulations. A new high level of performance for a linear shaped charge was validated.
Parametric Study of Exploding Foil Burst Phenomenon for Thin Flyer Impact Initiation of Explosives
In an Exploding Foil Initiator (EFI), thin polyimide flyer is accelerated at a velocity of 3-4 km/s by exploding metal foil, which bursts when high electrical energy is applied in short duration. The working of an EFI at low energy depends on many factors such as circuit parameters, characteristics of foil, flyer, barrel and types of explosive. Keeping the material, voltage, capacitance, length and width of foil constant, and varying foil thickness, parametric study of exploding foil is presented. When a large amount of electrical energy is deposited at very fast rate to fine bridge foil, it passes through the melting, boiling and vaporization phases up to the plasma state, giving off thermal energy and shock waves. In this work, the electrical Gurney Energy is calculated for estimation of flyer velocity using burst current density that defines action- integral characteristics of burst phenomenon. A MATLAB code is developed for studying variations in parameters and their interrelationships. The program computes foil burst parameters based on input values and thus helps in determination of exploding foil behavior. It is observed that keeping voltage 2 kV and charging capacitor capacity at 1 μF, as the thickness of exploding metal foil increases from 3 to 6 μm, the flyer velocity slightly increases, and remains constant up to 9 μm, thereafter, decreases marginally up to 13 micron, after which there is sharp decrease and no burst occurs at thickness greater than 20 micron. Also, for a given dimension of metal foil, the flyer velocity is highest for Gold material as compare to Copper and Aluminum. Experimental trials were carried out to establish parameters for successful working of EFI at low energy using an etched copper bridge foil. Experimental results are in good agreement with the results of the theoretical modeling using MATLAB, which will enable design of relatively low energy slapper detonator or explosive initiator for various applications.
Influence of the Embedded Structure on the EFP Formation of Compact Terminal Sensitive Projectile
To improve the damage efficiency of compact terminal sensitive projectile with EFP warhead, it is vital to understand how the embedded structure (ES) affects the EFP forming performance. In this paper, the corresponding numerical investigation is focused on, in which the fluid-structure interaction (FSI) method and the experimental verification are used. Based on the obtained quantitative relations between the forming performance and α (the ratio of height to maximum radius of ES), an optimal design is further provided. The results indicate that: when the embedded structural length and width range 0.1-0.3D and 0.1-0.2D (D: diameter of EFP warhead) at a fixed volume, respectively, EFP forming velocity nearly keeps as a constant, 1760 m/s; the height of ES has a dramatic effect on the propagating range of detonation wave, resulting in significant influence on the aerodynamic shape and length-to-diameter ratio of EFP; under the given constraints, the EFP length-diameter ratio can reach the optimal value 2.76, when the height of ES is 0.22D.
Tubular and Reconstituted Jets using Annular Shaped Charge Liners
Shaped charge liners having annular shapes have been examined to produce tubular and reconstituted jets. This effort included using the shock wave physics code ALEGRA and experimental testing. Experiments involved explosive charges (75/25 OCTOL) of 101 mm diameter with liners of OFHC copper having overall outer diameters of 76 mm. A ring initiator was used to initiate the explosives at various radii. The annular liners had shapes of hemi-toroidal shells located about the device axis. Results show that reasonably straight-walled tubular jets can be formed. Further, it was observed that a sufficiently large initiation radius could cause an inward jet flow to form a newly formed coherent jet on axis that we refer to as a “reconstitutedâ€ jet. A practical design is presented wherein on-axis jet and tubular jets can be produced on command from a single device. Thus, this annular shaped charge has multimode capability and can be used to attack armors through its on-axis jet or attack MOUT structures where large holes are produced by its tubular jet. The reconstituted jet has substantial length and 5 km/s velocity for direct and overhead attack applications.
Study on Formation and Penetration of Shaped Charge with Liner Vertex Initiation
A shaped charge was produced with liner vertex initiation that could form explosively formed projectile (EFP), the mechanism of EFP formation was analyzed, based on the energy conservation law and data from LS-DYNA numerical simulation, analytical models of EFP velocities and penetration depth of finite thickness armor target were obtained, finished the experimental verification with flash X-ray and long distance penetration of EFP, comparing theoretical calculation results with experimental ones, the errors of EFP velocities, length and penetration depth are only 3.6%, 4.1% and 5.3% respectively, the theoretical results are consistent with the simulative and experimental ones.
Experimental and Numerical Study of the Fragmentation of Warhead Casings
In this paper the combined numerical-experimental approach was used to investigate the explosively driven fragmentation of warhead casing . The experimental tests were conducted with the aim of gathering the data which will be useful for verification of the subsequent simulations. During the experiments after the detonation of explosive, the fragments of the ruptured casings were collected. The number and the mass distribution of fragments were examined. Then, the numerical simulations were conducted with the same explosive fragmentation geometry as in experiments. The correctness of the conducted simulations and the applicability of the used numerical technique were verified by comparing the numerical results, especially fragments number and their mass distribution, with the conducted experimental tests outcomes. The reasonable agreement between examined parameters was achieved, what testifies that the technique can be used in the future to predict the fragmentation behavior of warheads casings.
Role of Dispersion Model in Predicting Spatial Distribution of Fragmentation Warhead
Pre-formed fragmentation warheads are deployed to neutralize soft skin target. On detonation, fragments travel at high velocity and impact on target. Fragment spatial distribution depends on its velocity, direction and dispersion. One dimensional models of Gurney and Taylor (1940s) predict fragment velocity and direction, respectively. Dispersion in fragment direction is assumed to follow normal distribution. These models are modified independently over a period of time for catering two dimensional (edge) effects for better predictions of fragment spatial distribution. The paper presents, the comparative analysis of these models (with and without edge effects) for a warhead with a contour made in three sections - cylindrical, ogive and conical. Predictions are compared with the recorded fragment spatial distribution in test arena. It is observed that fragments disperse less at central portion of warhead. The set of equations catering edge effects predicts reasonable fragment spatial distribution with standard deviation of 3ï‚°.
Presented are the results of a study on a miniaturized design based on EFP (Explosively Formed Projectile) as a technical solution for the disruption of specific targets (pressurized pipes, gas cylinders…) with controlled collateral damages. The influence of dimensional factors, such as the liner geometry, the explosive mass and the casing thickness, was assessed by means of numerical simulations. A first series of tests was conducted on simplified surrogate target. The EFP formation was diagnosed by triple exposure flash X-rays. The results led to enhanced numerical models. A final numerical session was carried out to select two designs for the validation phase. This ultimate experimental session combined terminal performance with safety aspects. The study is original in that the mass of the EFP charge is under 6 grams including a liner with a diameter of 3 mm.
Viscoelastic Constitutive Model with Damages of Polymer-Bonded Explosives
Polymer-bonded explosives (PBXs) are complex viscoelastic materials exhibiting rate dependent and time dependent mechanical behavior which are largely influenced by the binder. Researching the response of PBXs is critical to developing an accurate constitutive model to address potential survivability, safety issues and design improvements. In this paper, a viscoelastic constitutive model based on actual damage mechanisms has been established to describe both the quasi-static response and dynamic response of polymer-bonded explosives (PBXs), which accounts for complex phenomenology including temperature, strain rate, and aging effects. Quasi-static uniaxial compression and tensile tests and split- Hopkinson pressure bar test have been modeling and simulation to study mechanical responses and damage evolutions of PBXs at different loading conditions.
Integration of an Over-Fly Top Attack Shaped Charge Jet within a Kinetic Energy Penetrator for Enhanced Multiple-Effects
The study investigated the feasibility of embedding a smear-compensated Over-fly Top Attack (OTA) shaped charge jet, within a penetrating Multiple Effects Warhead (MEW). 3D hydrocode modelling simulations considered a variety of design configurations, under static and dynamic engagements at different over-fly crossing velocities and stand-offs. The need to optimise space and maintain an anti-structures emplacement capability led to the design of a novel side-mounted initiation train. Experimental firings validated the initiation and two design variants, to form smear-compensated shaped charge jets. The 3D pre-trial hydrocode modelling simulations were verified with quantitative and qualitative analysis against ionisation probe, witness plate and multi-plane radiograph experimental results. The work has laid the foundation for follow-on de-risking and development, for progression to MEW anti-armour and anti-structures dynamic trials.
Analysis of Several Numerical Schemes for the Characterization of Solid Propellant Combustion
Prediction of solid propellant combustion behaviour is of major importance to guarantee its safety use. In this work, the application of some numerical schemes to solve propellant combustion problem is explored. These are MacCormack-TVD and Rusanov numerical schemes, which provide accurate results for other problems such as those described in [Liang et al., 2006] and [Otón-Martinez, R.A. et al., 2015] respectively. They are different from those traditionally used in the studied literature on this subject: the two-step predictorcorrector numerical integration scheme developed by Mac-Cormack or Lax and Wendroff numerical schemes which have been traditionally used to solve the set of coupled and inhomogeneous differential equations [Hoffman and Krier, 1980] and [Gokhale and Krier, 1982]. The computed results are deeply discussed. The influence of considering a modified solid phase momentum equation to assure that void fraction do not decrease under a lower margin is analysed. Finally, some conclusions are drawn.
Modeling of Thermal Reactions and Associated Events
Thermal stimuli through slow cook-off heating are particularly interesting, since underlying phenomena are very complex, responses depend upon various parameters and they may have a significant impact on warhead system design. A standardized test device with cast-cured or pressed plastic-bonded high explosive charges is used at TDW for investigating such slow thermal stimuli that allows evaluating reaction levels and decomposition temperatures of high explosives. It provides a confined environment and also permits temperature measurements inside the high explosive charge. Experimental tests results of KS57, KS22, and P31 charges varied between burn and deflagration reactions depending on high explosive charges and charge confinements. Such experimental data provide a profound basis for thermal modeling of slow cook-off responses. Multi-physics coupling of transient heat conduction with Arrhenius reaction kinetics form a system of coupled partial differential equations. AKTS-Thermokinetics software deliver corresponding input functions that were determined through differential scanning calorimetry tests of small explosive samples. The recently enhanced model implemented in MATLAB considers additional boundary conditions such as heat conduction through the casing, convection of the turbulent oven heat flow into the casing, and end cap venting effects. Predicted self-heating times, rates, and peak temperatures approach well experimental data. Using this proposed multi-physics model in finite element simulations like COMSOL provides spatial temperature distributions over time and allows future application to full-scale warheads.
Investigation of Interior Ballistic Initial Conditions in ALE3D for Blast Overpressure Analyses
We explore two initial conditions on the same numerical grid to simulate blast overpressure at crew locations in the far-field. The first utilizes a 2D axisymmetric simulation mapped into a 3D quarter symmetry domain (2D-IC) as an initial condition for the exterior blast overpressure simulation. The purpose of this method is to reduce runtime from days to hours where the simulation lends itself to axisymmetric (i.e. the interior of a cannon). The second utilizes a full 3D quarter symmetry simulation (3D-IC) started from propellant ignition to propagation to the position of interest in the exterior of the tube. These results are then compared to experimental blast overpressure results for the same position. The conclusions from the study are that both the 2D-IC and 3D-IC are valid methods for numerically determining blast overpressure. However, the two initial condition approaches vary significantly compared to one another.
Projectile Formation of Tantalum EFP Liner Fabricated by Thermo-Mechanical Processes
As explosively formed penetrator materials, tantalum has been the subject of intense studies due to its high density and good formability. It is known that mechanical and physical properties of tantalum are significantly affected by crystallographic texture. While considerable work has been carried out and much is known about the development of texture in deformed and recrystallized tantalum, it is not clearly known about the effect of tantalum texture on EFP formation. In this study, projectile formation behavior of tantalum EFP liners with various textures was examined. Tantalum EFP liners were fabricated by thermo-mechanical processes. The influence of the processing route on the recrystallized texture and microstructure was analyzed. Shapes of explosively formed penetrators of thermo-mechanically processed tantalum liners were examined by flash X-ray radiography.
Scaled Demonstration of a Momentum Cancelling Active Blast Mitigation Concept
An active mitigation countermeasure, based on the principle of momentum cancellation of detonating counter-charges against the effect of explosive blast, has been researched. The study was conducted on a small scale and then extrapolated to an intermediate scale. On a small scale it was demonstrated, both theoretically and experimentally, that high orders of momentum cancellation are achievable. Good correlation was obtained between the numerical predictions and the experimental results. Similarly, on the intermediate scale, with a specific choice of experimental setup, good correlation was achieved between the numerical and experimental results. The differences between the results of the small scale and intermediate scale investigations are attributed to variations in the verification methodologies.
Modeling Fragmentation Performance of Large L/D (Length over Diameter) Explosively Driven Metal Shells
New advanced numerical computer model enabling accurate simulation of fragmentation parameters of large L/D explosively driven metal shells has been developed and validated. The newly developed large L/D multi-region model links three-dimensional axisymmetric high strain high strain-rate hydrocode analyses with the conventional set of Picatinny Arsenal FRAGmentation (PAFRAG) simulation routines. The standard PAFRAG modeling technique is based on the Mott’s theory of break-up of idealized cylindrical “ring-bombsâ€, in which the length of the average fragment is a function of the radius and velocity of the shell at the moment of break-up, and the mechanical properties of the metal. In the newly developed multi-region model, each of the shell region, the break-up is assumed to occur instantaneously, whereas the entire shell is modeled to fragment at multiple times, according to the number of the regions considered. According to PAFRAG methodology, the required input for both the natural and the controlled fragmentation models including the geometry and the velocity of the shell at moment of break-up had been provided from the hydrocode analyses and validated with available experimental data. The newly developed large L/D multi-region PAFRAG model has been shown to accurately reproduce available experimental fragmentation data.
Shock Compression Properties Theoretical Calculation of MESMS with the Effect of Thermal Motion of Electrons
Based on the high pressure equation of state (EOS) and atomic statistical model, the influence of the electronic thermal motion on the shock compression behavior of the material are investigated. The parameter R is derived according to the high pressure equation of state Wu-Jing model. Meanwhile, the high pressure EOS for the porous metals with the effect of electronic thermal motion is proposed. Taking Cu material and the typical mixed material W/Cu alloy as the examples, the shock compression behavior are calculated under different porosity. Compared with results without the effect of electronic thermal motion, it shows that the influence can be ignored under low pressure and low porosity. With the enhancement of pressure and porosity, the effect of electronic thermal motion becomes obvious.
Statistical Variations in Blast Loads from Buried Explosives
Five nominally identical blast-loading tests were conducted where dynamic deflection data was collected. The dynamic deformation data collected was of the upper surface of a blastloaded hull shape. This data allowed the determination of the initial velocity imparted to each point of the surface in the first 1 or 2 milliseconds of the blast event. Analysis of this data showed that the spatial variation of the normalized blast loading is small, in particular it is less than 5%. Larger variations occur for the total blast impulse. Thus, the spatial distribution of the blast event (when normalized by the initial impulse) has less variation and is more repeatable than the actual total impulse of a blast event.
Numerical Simulation Research on the Effect of Radial Rotation on the Formation of Explosive Forming Projectile
In order to study the forming condition of EFP under radial rotation, the numerical simulation of typical explosively-formed projectile (EFP) charge structure in different positions and rotational speeds are completed by using the finite element simulation software LS-DYNA. Simulation results are verified preliminarily by experiments. Results show that the EFP formed under the radial rotation condition has the lateral deflection speed, and the shape is asymmetrical. When the tip of the EFP has horizontal diversion, the tail of the EFP has vertical diversion, and the infection of radial rotation is most seriously, while the rotation location is in the bottom with middle and the donated pointed rotation location followed. Research results also provide a good example for the study of EFP under the radial rotation condition.
Analysis of Staircase Reliability Tests with Least Square Method
The design of stair-case tests is straightforward in mathematical terms, but it may be timeconsuming and cost-sensitive in actual engineering applications. The strict requirement for constant step intervals between each trial and assumption of step interval value often repre-sents a considerable engineering challenge. The flexibility of the method presented in the current study allows its application for staircase tests with variable step intervals between trials. The method is based on classical Least Square Method and its final outputs are approximations of mean (X50) value and its standard deviation, similar to the Bruceton approach. The algorithm presented overcomes uncertainty about its data and distribution type, and leads to applicable engineering results.
Air Blast from a Moving Charge on a Moving Target
Numerical study was conducted to analyze the effect of a moving charge on a stationary target. As was found earlier, the shock wave emanating from the moving charge is spherical although the pressures in the direction of movement are much greater than those in the opposite one. The analysis was conducted by running Autodyn 2D and 3D, assuming the target is rigid and either stationary or moves parallel to the charge. The reflected pressures and the overall force on the target were measured for a moving 1 Kg charge at various velocities. The results show that the load on the target increases significantly if the explosion is in air and the intensity of this load depends strongly on the charge velocity.
A Computational Framework for the Design and Optimization of Explosives
An optimization framework was developed as a step toward automating the design of explosive devices. The Sandia National Laboratory codes Dakota and CTH were coupled to optimize the kinetic energy output of a one dimensional exploding cylinder. Three configurations of TNT explosives were considered, an aluminum case with a variable outer radius and wall thickness, a composite aluminum-iron sandwich case with a fixed radius and variable wall thicknesses, and a model with varying wall material and thickness. Dakota successfully optimized each design using a suite of optimization algorithms. A energy-based nondimensionalization scheme was also developed to explore the CTH and Gurney equation models in more detail.
Using Nickel-Tungsten Alloys to Produce Multiple Explosively Formed Penetrator (MEFP) Warheads
In an effort to find an alternative to tantalum for use in multiple explosively formed penetrator (MEFP) liners, the U.S. Army Armament Research, Development and Engineering Center, Picatinny Arsenal, N.J., fabricated, simulated, and tested liner blanks from pure nickel, a two phase tungstennickel- iron alloy, and a single phase nickel-tungsten alloy. Overall, there were two design iterations comprising seven distinct MEFP liner geometries that resulted in 12 experimental warhead tests. The first iteration of testing (five tests) successfully formed single piece MEFP penetrators, except for the nickel-tungsten alloy. The second iteration (seven tests) produced a successful pure nickel MEFP design, but unsuccessful tungsten-nickel alloy designs. Based on the results, it was revealed that the material model had been calibrated incorrectly. The most probable reason for this was that the strength parameters were increased too much. In the future, any MEFP warhead development using these particular alloys should be undertaken only after generating more accurate models for these two materials.
Exploring the V2D Initiation Criterion within the Lee-Tarver Model
Shock initiation of explosives has been at the focus of many important studies over the years. One of the interesting topics in this field deals with the ability of a projectile, or jet, to initiate an explosive through impact. To this end, Held introduced the critical v2d initiation criterion, which has shown great success for the case of bare explosives. However, recent experimental results have questioned the generality of this criterion for cases of covered explosives. In this work we employ the Lee-Tarver model, to numerically explore the shock initiation of PBX9404 explosive, subjected to the impact of long rods. We demonstrate the generic difference between bare and covered explosives and identify the crossover between these two cases. We conclude by mapping the run to detonation distance, for rods of different velocities and diameters, for covered explosives.
The Mechanism of Variable Thickness Conical Shell Fragments’ Fracture Modes and Morphological Characteristics
This paper presents a study of fragments’ fracture modes and morphological characteristics for fragmenting variable thickness conical shell under internal explosive loading. Available research focus on the constant thickness shell, and very few researches or articles are described to research variable thickness conical shell. Fragmentation of such shell was investigated experimentally, and the fragments' fracture modes and morphological characteristics were obtained by observation and statistical analysis. Then, the mechanism was studied, which is related to the interaction between adjacent longitudinal cracks. According to the research results, there are significant differences in the fracture relative time difference of the longitudinal positions of variable thickness shell when the position of initiation end is different. And it will lead to that if the position of initiation end is small end, the range of pure shear fracture zone is much larger than initiation from the big end, while the shape of the fragments is also more inclined to long strip.
Analysis of the Effect of the Altitude of the Damage Effect of Plates Subjected to Explosion Blast Wave
Make establishment of the parameters of ideal gas model of different altitudes air. Using the linear numerical analysis software AUTODYN to calculate the blast overpressure and impulse of different altitude environments. Make assessment of damage level of plate subjected to explosion blast by meaning of over-pressure criteria. The results show that the altitude effect on the plate’s damage subjected to explosion blast is significant and should not be ignored.
Fast Running Methods for Penetration Processes in Masonry Materials
Current military operations often comprise urban scenarios. Thus, masonry objects offer protection and shielding against weapon effects. To effectively engage enemy forces and targets the munitions applied must be capable of perforating masonry materials and of delivering lethal force behind structures. Building structures may consist of soft materials like clay or adobe as well as of hard materials like brick or (reinforced) concrete. They might be set up of double or triple layers in combination with mortar opposing a very inhomogeneous target compared to classic armored vehicles. The penetration of these structures by small and medium caliber projectiles results in projectile deflection and tumbling. Also large shot to shot scatter of residual velocities is associated with these nonlinear trajectories, as has been observed in penetration testing and high-fidelity numerical simulations (such as FEM). The prediction of weapon effects with standard accredited vulnerability tools, like UniVeMo (Universelles Verwundbarkeitsmodell) in Germany, has to consider the observed effects but also has to provide results in acceptable time frames. Therefore fast-running methods have to be developed. This presentation will demonstrate the IABG approach deriving regression functions and/or look-up tables for small and mid-caliber penetration processes in masonry materials. Based on numerous simulation and experimental results the phenomena observed will be described, the way to fast running modules including the application of analytical tools will be explained, and final results and samples will be demonstrated.
An Investigation of Armor Bolt Failure due to Ballistic Events
Military vehicle armor panels are traditionally mounted through the use of bolts. A proper understanding of bolt loading conditions and failure is necessary to produce an optimal attachment design. Bolt failure during a ballistic event could lead to vehicle vulnerabilities. Tank-Automotive Research, Development, and Engineering Center (TARDEC) and Southwest Research Institute (SwRI) performed a study quantify the forces in the bolts and understand the failure mechanisms of bolts. This was successfully achieved using instrumented bolts and various tensile tests. The results will be used to develop design guidance for vehicle integrators. This paper summarizes the testing that occurred and the results of the effort.
Numerical Analysis of Rifle Bullet Impact Armor Covered Human Torso
To study the behind armor ballistic trauma (BABT), a finite element model of human torso has been developed based on the CT data of a Chinese adult man. The model consists of organs system (heart, lungs, liver and stomach), skeleton system (sternum, costicartilage, ribs and spine), mediastinum and skin. The experiments of rifle bullet penetrating ceramic/ultrahigh molecular weight polyethylene (UHMWPE) laminate composite body armor combined with soft body armor were conducted to verify the accuracy of the numerical model. The skeletal structure was assumed to be linear-elastic while all internal organs were modeled as viscoelastic. The impact responses of armor covered human torso under the penetration of rifle bullet at different impact point were conducted numerically. The pressure time histories of heart, lung, liver, stomach were obtained. Furthermore, the contours of von Mises stress in the skin, thoracic cage and internal organs were also analyzed. The numeric model provides an effective method to study internal organ injuries and design better vests under non-penetrating ballistic impact.
On the Ultimate Potential of High Strength Polymeric Fibers to Reduce Armor Weight
The capability of polymeric fiber based composites to stop ballistic projectiles at low armor weight is predominantly related to the specific tensile strength of the fibers. This paper and presentation discusses the ultimate theoretical and experimental specific tensile strength of various polymeric fibers (polyethylene, para-aramids, rigid-rods, graphene). It is concluded that the realistic achievable strength of these fiber systems is about half the theoretical strength of single atomic bonds. Ultimate experimental strengths of most fiber systems have reached almost 50 % of this realistic achievable strength. Considering that no defect structures have yet been incorporated in this theoretical strength, it is postulated that these fibers strength can not be increased strongly anymore. Polyethylene fibers, like Dyneema®, have the highest experimental specific fibers strength of all fibers, which would enable a reduction in armor weight by 40% of the current best polyethylene fiber based armor.
Structure Optimization of Projectile during Highspeed Normal Penetrating Considering Bending Failure
In order to study the bending failure of projectile during high-speed normal penetration into concrete, a dimensionless bending factor is introduced according to the failure modes of projectile, and the dimensionless stress of dangerous cross section is calculated according to Forrestal’s resistance formula. Further, bending failure criterion of the normal penetrating projectile is proposed, i.e., when dimensionless bending factor is greater than 6.8 and dimensionless stress of dangerous cross section is greater than 0.70, the bending failure of the projectile occurs. According to the failure criterion and the no upsetting condition of hollow part, optimization of maximum charge volume and the corresponding projectile structure without bending failure are given, then, the bending failure criterion and the optimized structure of the projectile are verified by numerical simulation.
Numerical Analysis of Penetration Reduction of a Long Rod Penetrator Impacted by a Linear Explosively Formed Penetrator
In this study, the collision effect against a long rod penetrator by a linear explosively formed penetrator (LEFP) was investigated through a series of numerical analyses. LS-DYNA, a nonlinear finite element analysis code, and the multi-material ALE technique were used to conduct the analysis containing a collision into a long rod penetrator with L/D=10.7 and an initial velocity of 1,600 m/s by an LEFP and subsequent residual penetration into RHA steel by the long rod penetrator. Some combinations of hit locations and hit angles by the LEFP against the long rod penetrator were composed to formulate possible collision conditions. Under such conditions, DOP reductions by the rod penetrator damaged by the LEFP were predicted as considerable, and the reasons why such DOP reductions were achieved were discussed on the basis of the behavior of the deformed rod penetrator after impact by an LEFP.
Ballistic Performance of Ceramic Targets against 25mm APDS-T Projectile
Tungsten based heavy alloys (WA), used as penetrators, constitute a major threat. An experimental and numerical investigation was performed to study the ballistic performance of alumina tile-based composite targets in an effort to generate data for certain high performance WA projectile. The experiments were conducted using tungsten-alloy projectiles of 25x137mmAPDS-T (M791) at a striking velocity of 1260 m/s. This heavy metal projectile has high strength and is relatively ductile. It is, therefore, difficult to apply on the projectile model structural cracking, breakage or fragmentation, even upon oblique impact that generates asymmetric forces. In order to find an effective mechanism that will defeat such projectiles, it is necessary to develop numerical models simulating the behavior of the projectile during the penetration process. The ceramic tiles used for this study were backed by 80 mm RHA steel blocks. The residual depth of penetration in the RHA block was used as a reference measure for the resistance of the ceramic targets to ballistic penetration. This study consists of three phases: the first examined the influence of confinement of the ceramic tiles on the ballistic performance. The second examined the efficacy of adding a cover plate. The third examined the effect of laminated structures on the effectiveness of ballistic ceramic tiles. In general, each of these configurations is known to be effective in enhancing the resistance of the ceramic target. For a reference to the simulations, several ceramic penetration theories which are available and published in the literature, Refs. [1]-[5], were used and discussed.
This paper will discuss normal projectile impacts on wood. Impact experiments have been performed using flat wooden targets with different physical properties. Materials of different hardness have been selected, viz. Douglas, European Pine, European Oak, Merbau, Bangkirai, and Azobe. Three different 9 mm projectiles are used, viz. Ball, Action NP and Ball Subsonic. Penetration depths of projectiles are determined using x-ray photography. The experimental data are analysed using both the Robins-Euler model and the Poncelet model. This implies that the resistance to penetration offered by the wood can be resolved using two physically interpretable components, viz. the contribution of inertial stresses and the dynamic strength of the material. The penetration depths of the projectiles are related to physical properties of the wood. The dynamic strength Rt derived from the models shows a good correlation with the Janka hardness of the wooden targets. Finally, future research is discussed.
On Temperatures in Shaped-Charge Jet Penetration
Jet and target temperatures during penetration are computed using the compressible jetpenetration model of Flis [1] for several materials. The model considers only the hydrodynamic compression work and shock heating and neglects plastic-work, phase-change, and heat-conduction effects. The model is here extended to predict also the residual jet and target temperatures after return to ambient pressure. Previously measured temperatures of projected jets are taken as initial jet conditions for the penetration. The model predicts that temperatures exceeding 2000 K may be reached in targets at practical shaped-charge-jet velocities. Much more of the temperature increase in more compressible materials (polymers and liquids) at high jet velocities is attributable to shock heating than to isentropic compression work behind the shock. The temperature increase in the jet depends strongly on its initial temperature.
Analysis of Temperature Rise on the Projectiles’ Surface Including the Mass Abrasion Effect
Based on the experimental observations and analysis, the evolution mechanisms of mass loss process induced by plastic deformation and high temperature during penetration were proposed. A thermal dynamic mass loss model is proposed to investigate the mass loss based on the mechanisms of thermoplastic failure. Combining the temperature rise generated from the friction work and the plastic deformation work during the high-speed penetration process, the gradient distribution of the temperature change along the depth from the surface of a projectile is predicted. Through the comparison of the percentages of heat generated with different mechanisms at different locations of the projectile, the dominant mechanism of the mass loss between the friction and plastic deformation is analyzed to get an insight into the high-speed penetration process.
Multi-Scale Experiments on Soft Body Armors under Projectile Normal Impact
Soft body armors have been widely used by law-enforcement and military personnel. However, predictive capabilities on the critical conditions for the impact failure of these armors are still not well-developed. This article summarizes our recent experimental research efforts aimed at developing a better understanding of impact failure of soft body armors at several size scales, ranging from shoot packs, single-plies, yarns, and fibers. The experiments reveal that impact resistance of packets is dictated by axial properties and shear strength of the textile materials, as well as structural properties such as weave patterns. At the single-ply level, the critical impact velocity depends heavily on the nose shape of the projectiles, as well as the axial and transverse properties of the yarns. The failure of yarns and fibers depends on the stress state, as interpreted from the effects of nose shapes of the indenters and from the application of multi-axial stress states. The effects of aging on the impact resistance is also discussed.
Study of High-Speed Aluminum Rod Non-Destructive Recovery Device
A soft medium recovery device has been designed and studied. Within the velocity range of 800â€1200m/sec, the high-speed aluminum flat head rods were used for nonâ€destructive recovery by flour medium. We obtained the drag coefficient of aluminum flat head rod in flour. In addition, the velocity decay curve of instantaneous penetration velocity above the critical speed was also measured. It can provide an important and helpful theoretical guideline for non-destructive recovery of high-speed projectiles and soft-recovery device design. Furthermore, the study can be used to complete the research of soft-recovery recovery device for high-speed aluminum rod.
Comparison of Numerical Modeling of Penetration of a Capped Projectile with a Windscreen into Special Treatment Steel with Traditional Formulae
The penetration of Armor Piercing, Capped (APC) projectiles into Special Treatment Steel is not new [1]. Many years ago the means of calculating the ballistic limit, residual velocity, etc. were based on semi-empirical formulae garnered from actual tests [2]. Major geometric changes in the design of a projectile, cap and windscreen made some difference in the ability of the shell to penetrate armor plate. The purpose of this paper is to attempt to determine a reasonable method to model the mechanical properties of the target material as well as the projectile components to reasonably match the test data and compare with the semi-empirical models. The projectile chosen is a U.S. Navy 14 inch Mark 16 Model 8 projectile depicted in Figure 1. This projectile has been modeled using the Abaqus finite element software. It is believed that the triaxiality of the target material has a great effect on the results [3]. This was compared to the semi-empirical formulae of Lambert and Thompson as well as that of Okun [4]. The modifications to the mechanical properties in the Abaqus model to incorporate triaxiality are discussed. The models were in very good agreement over a fair range of target thicknesses and impact obliquities but not at high obliquities and large target thicknesses.
Experiment Study on Anti-Penetration Peformance of Liquid Composite Armor to Shapedcharged Jet
This paper focuses on the anti-penetration performance of liquid composite armor and fluid viscosity influence on anti-penetration performance of liquid composite armor. The concept of STF as filler of liquid composite armor subject to shaped charge jet (SCJ) is presented in this paper, and these liquid are water, ploy ethylene glycol of 200 molecule mass (PEG200), two kinds of STF. Firstly, rheological experiment on four kinds of liquid was carried out to obtain the viscosity vs. shear rate curve. Secondly, depth of penetration (DOP) experiments of liquid composite armor containing four different liquid subjecting to Φ56mm shaped charge (SC) were carried out. Furthermore, one reference DOP experiment with steel target was also carried out. Based on the data of rheological and DOP experiment, the protective performance of different liquid composite armor was analyzed, moreover the influence of liquid viscosity on the anti-penetration performance was discussed.
New Approaches to Modeling and Simulation of Ultra High Molecular Weight Polyethylene
This work deals with numerical simulations of impact problems on fiber-based composite armor using the commercial finite-element-code ANSYS AUTODYN. Having presented some basic knowledge on the theory of numerical simulation in AUTODYN, two recently published approaches for modeling impact on the selected composite (Dyneema® HB26) are explained. While both of them make use of a nonlinear-orthotropic material model implemented in the AUTODYN-code, they differ in the way how the highly inhomogeneous microstructure of HB26 is represented geometrically. Lässig chooses a fully homogeneous description, whereas Nguyen discretizes the composite into sublaminates, which are kinematically joined at the surfaces and breakable when a certain contact-stress is reached. In order to validate the two approaches, the response of HB26- samples impacted by handgun-projectiles was determined experimentally and compared to the corresponding numerical results. Unfortunately, a poor agreement between experimental and numerical results was found, which gave rise to the development of an alternative modeling approach. In doing so, the composite was subdivided into alternating layers of two different types. While the first type of layers was modeled with open-literature properties of UHMWPEfibers, polymer-matrix-behavior was assigned to the second type. Having adjusted some of the parameters, good agreement between experiment and simulation was found with respect to residual velocity and depth of penetration for the considered impact situations.
Research on Armor Debris Cloud Characteristics of Shaped Charge Jet Penetrating Target Vertically
When shaped charge jet (SCJ) penetrating finite thickness target, penetration depth and armor debris cloud are major determinants of damage degree. Especially for the interior equipment and personal of armor vehicle, extent of damage mainly related to the armor debris cloud distribution characteristics. A great number of studies on armor debris cloud that generated by SCJ have been done by domestic and foreign scholars. Research methods on this issue have mainly concentrated on numerical calculation and experiment. Therefore, it is not satisfied due to the formation mechanism analysis on the armor debris cloud lacked. In this paper, the debris cloud that generated during the process of SCJ penetrating target was divided into three parts - front, middle and rear. Theory analysis on the armor debris cloud formation mechanism, space and velocity distribution had been preliminarily studied based on the propagation character of shockwave and penetration characteristic of jet penetration on target. The theoretical calculation results are in good agreement with experimental results of X-Ray imaging test.
Research of Wave Interaction for Multiple Jet Penetration into Concrete
Multiple shaped charges penetration into concrete has been investigated with experiments and simulations have been conducted in the past several years. However, the theoretical research on multi-jet penetration into concrete has not been reported yet. Based on the characteristics of shaped charge jet penetration into concrete, the formation and propagation of shock wave created by shaped charge jet penetration concrete is analyzed in this paper. The radial stress and tangential stress are obtained by crater stagnation pressure and radial crater growth velocity as the radius increases. Moreover, a theoretical model of wave interaction for multiple jets penetration into concrete is also presented in this paper, furthermore the appearance and evolution of crack on the concrete target is discussed. Experiments of four shaped charges penetration concrete were performed to verify theoretical analysis. It is shown that large crater was formed by both two kinds of multiple shaped charges. Theoretical calculations are well agreement with experiments.
Deceleration-Time Data for the Verification of Calculation Models of the Penetration with Erosion in Target
Primary experimental data recorded according to piezometric technology, such as: oscillograms of the elongated steel rods deceleration history in the steel targets was previously presented in the papers published at the 25th, 26th, 27th and 29th ISB. Data was being continuously recorded from the beginning to the end of collision within the range of impact velocities from 1000 to 1500 m/s using a special version of piezometric technology. The rods of various elongations were penetrating into the target with different erosion degrees in the implemented initial impact conditions. The possibilities of further processing of records for verification of collision processes computational models of steel rods and steel targets within the speed range accomplished in the experiments are proposed in this paper by the example of the previously published primary acceleration-time experimental data.
Investigating the Mechanical Properties of Rheological Materials for Flexible Body Armour
The paper describes the rheological tests of three materials: the silicone elastomer, the shear thickening fluid STF and the commercial shear thickening polymer which are planned to be used as elements of the bulletproof vests as well as in the high impact protective equipment. In plate-plate configuration two kinds of tests were carried out. In the static mode the dependance of shear stress τ and viscosity η on shear rate ðœ¸Ì‡ was investigated wile in the dynamic mode storage modulus G’, loss modulus G’’ and complex modulus G* were determined. On the basis of the recorded values in the first test flow curves and viscosity curves for materials were drawn up. The dynamic tests defined what properties (elastic or viscous) are predominant in the materials for given loads and which material exhibits the most desirable characteristics with respect to the intended application.
ABSTRACT: This paper describes a novel approach taken to modelling the water-jet disruption process for neutralising improvised explosive devices (IEDs). QinetiQ’s proprietary Eulerian hydrocode, GRIM, has been used to identify methods of generating fast-running models of water-jets. Experimental data from energetic trials conducted by Dstl have driven model optimisation to simulate on-target effects of explosively driven water-jet disruptors. These first generation models for improvised explosive device disposal (IEDD) have made significant progress in predicting the impulse delivered to a target and the penetration performance. These models will assist the development of a fastrunning IEDD analysis tool which will aid the design and evolution of current and future disruptors.
Extended Abstract - Comparison of Backing Materials Used in the Testing of Ballistic Body Armour
This paper provides a summary of a comparative study of three different backing materials that can be used for ballistic testing of body armour. The study used standardised test packs, shot patterns, velocities and test rounds to build a data set. The aim being to understand how these mediums work and their use in the assessment of behind armour blunt trauma. In addition, the data set enables the variance of the different mediums to be greater understood. This is an extended abstract paper and associated poster summarising initial results of work conducted as part of my PhD at Cranfield University. The full paper is planned to be published in early 2018.
Comparison of the DM11A1B2 9mm Luger FMJ Bullet from Two Different Manufacturers
Currently the certification of UK ballistic resistant police body armour is determined according to HOSDB Body Armour Standards (2007). The test round DM11A1B2 manufactured by Dynamit Nobel is used to assess handgun protection (levels HG1A, HG1 and HG2). This round has proven consistent performance; however, Dynamit Nobel has ceased manufacture of the DM11A1B2 and an alternative test round was required. It was identified that Metallwerk Elisenhütte GmbH (MEN)had manufactured a DM11 A1B2 9mm FMJ Luger which appeared to be the same as the one previously supplied by Dynamit Nobel. However, it became apparent after initial testing that the bullet performance against body armour compared to the current test round varied. This paper presents the work that has been carried out to date to investigate why this discrepancy in performance exists. The comparison included dimensional measurements, micro hardness testing, scanning electron microscopy analysis and elemental analysis.
Numerical Analysis of Behavior of the Nanostructured Bainitic Steel used in Armor
Numerical model of 12.7 mm type B-32 projectile and high-strength samples of NANOSBA bainitic steel with hardness of 47 HRC were developed, tested and verified with experiment. Computer codes were adapted and modified using the free points method in version with so-called markers. It referred to a new method of maintaining of the calculation stability and proper selection of weighting factors for calculation of velocity gradients and stresses in the contact areas of materials with different properties. The basic criterion of the numerical model correctness was the shape and depth of penetration of the Armox 500T armor plate on which the bainitic steel samples were placed and fired with the 12.7 mm type B-32 projectile with velocity of 850 m/s. A satisfactory agreement was obtained of the theoretical results with firing tests of the samples, i.e. size and shape of craters in the Armox 500T plate.
Measurement of Bullet Impact Conditions Using Automated In-Flight Photography System
Knowledge of impact conditions is critical to evaluating the terminal impact performance of a projectile. For a small caliber bullet, in-flight velocity has been precisely measured for decades using detection screens, but accurately quantifying the orientation of the bullet on a target has been more challenging. This report introduces the Automated Small-Arms Photogrammetry (ASAP) analysis method used to measure, model, and predict the orientation of a small caliber bullet before reaching an impact surface. ASAP uses advanced hardware developed by Sydor Technologies to record a series of infrared digital photographs. Individual images (four orthogonal pairs) are processed using computer vision algorithms to quantify the orientation of the projectile and re-project its precise position and orientation into a three-dimensional muzzle-fixed coordinate system. An epicyclic motion model is fit to the measured data, and the epicyclic motion is extrapolated to the target location. Analysis results are fairly immediate and may be reviewed during testing. Proveout demonstrations have shown that the impact-angle prediction capability is less than six hundredths of a degree for the 5.56mm ball round tested.
The Analysis of the Possibility of the Use of Composites Panels with Graphene as Protective Layers
The article presents the use of graphene in form of sheets with dimensions of 90×100 mm in multilayer composite panels manufacturing. The panels have been made from the carbonepoxy prepregs material with the use of out of autoclave technology. The results of ultrasonic non-destructive tests of composite panels with and without graphene were presented. Performing the tests in accordance with ASTM procedure, the impact resistance of composite panels with and without graphene was determined. Additionally, the article presents the results of residual compressive strength after the impact test of carbon-epoxy composites with and without graphene with the compression speed of 0.005 mm/s. From the analysis of the images taken during the impact test, the energy dissipation during the time of experiment was determined by measuring of the length of crack propagation. On the basis of the own investigation of graphene protection panels and the studies presented in the literature, possible future applications within this field were presented.
Spall and Fracture in 3D Simulations of Penetration Tests into Al7075 Plates
In the current study we demonstrate numerical representation of penetration into brittle target. A copper projectile was launched at a velocity of 2000 m/s, towards a thick 7075- T651 aluminum target. The penetration process resulted in the fracture of the target plates as the projectile remnants perforated them. Numerical simulations of the event were performed using simplified constitutive models. The brittle failure model, characterized by a single parameter criterion, was introduced in order to model a brittle fracture and spall if the target.. The spall criterion was adjusted until agreement between the fracture pattern of the numerical model and the target. We found that a single parameter criterion is sufficient for an acceptable representation of the spalling and fracture of the plates. Furthermore, the value of the spall stress is lower than the values reported in literature and that it is mesh size dependent.
Application of the RHT Concrete Model for Predictive Simulations of the Penetration into Adobe Targets
In the present paper, we review and extend our results concerning predictive numerical simulations of the penetration into adobe on the basis of the RHT concrete model [C. Sauer et al., Int. J. Impact Engng., 104 (2017) 164-176]. We apply this model to the theoretical description of adobe in a hydrocode. For this purpose a set of material parameters is derived on the basis of published data, own material tests, and engineering assumptions. Available ballistic results for the penetration of spherical steel projectiles into semi-infinite and finitethickness adobe targets are used for validating our approach. As a result, we obtain a hydrocode model which is expected to predict a wide range of penetration scenarios into adobe. The predictive character is exemplarily demonstrated by the successful reproduction of the instability within the penetration process and residual velocities of differently shaped tungsten heavy alloy projectiles.
High Strain Rate Deformation of W-Ni-Fe Alloys.
Tungsten heavy alloys are widely used in ballistic applications due to their superior mechanical properties. The deformation characteristics of tungsten heavy alloys at high strain rates should be determined to understand the perforation and penetration performances. One of the ways which is commonly used in determining the deformation behavior of the alloys at high strain rates is Taylor impact test. In this work, the dynamic properties and deformation characteristics of 93W-5.6Ni-1.4Fe and 93W-4.67Ni-2.33Fe alloys were investigated by Taylor impact tests with different velocities by using a single stage gas gun. The samples were cold isostatically pressed under 300 MPa and sintered at 1460ºC and 1480ºC for 20 minutes under hydrogen and 10 minutes under argon atmosphere. Numerical analyses of Taylor tests were conducted by using Autodyn 3D to compare with the test results. The study showed that, the samples which were sintered at 1480ºC had more plastic deformation in Taylor impact tests and good agreement in deformation characteristics of test and numerical results of low velocity impact was obtained.
Flexible Bulletproof Armor with Modular Interlayer
The paper describes bulletproof tests of flexible armors containing different variants of modular interlayers. This elements were placed in the armor between the textile layers of the ultra high molecular weight polyethylene (UHMWPE). The interlayers were made of the rheological materials: the silicone elastomer (composition of methyl-, phenyl-, borosiloxane polymers with addition of fillers and lubricating mediums), the shear thickening fluid STF (silica nanoparticles dispersed in polypropylene glycol) and the commercial shear thickening polymer as well as the same polyethylene layers which were sewn or ultrasonically welded. Before performing the bulletproof tests in order to select the most appropriate process parameters and to compare the process to other ways of combining polyethylene layers the strength tests of ultrasonically welded joints were carried out. Different variants of ultrasonically welded protective layers were made. The samples with dimensions 400x400 mm were tested with the use of the 0.44 Magnum SJHP bullet.
Experimental High Velocity Impacts through Float Glass and Pyrex® Plates
27 gas gun trials were performed to assess the performances of float glass and Pyrex® plates to mitigate fragments. During these trials, stainless steel 304L, tantalum and Densimet® 176 rods were fired against float glass and Pyrex® plates. The aspect ratio (L/D) of projectiles ranged from 0.2 to 5 and the impact velocity was either 900 m/s or 1700 m/s. Two 150 kV X-ray heads were positioned 100 mm and 200 mm behind the glass plate to visualize the shape of the projectile and measure its residual velocity. Aluminum 7175 (for steel projectiles) and steel S690 (for tantalum and Densimet® projectiles) witness plates were positioned 400 mm behind the glass plate to stop the projectile. For each trial, projectile residual velocity, projectile shape and damage in the witness plate constituted a consistent set of data to assess the performances of glass mitigation plates against the fragment threat.
Reliability Analysis of Long-Rod Penetration Using the Walker-Anderson Penetration Model
This paper addresses reliability assessment of the long-rod penetration for semi-infinite target to quantify the effect of uncertainties such as impact velocity, shape design, and material properties of projectile and target. For this purpose, the inverse reliability analysis is performed to calculate most probable point (MPP) for limit state function of the normalized penetration depth based on the performance measure approach (PMA) with the hybrid mean value (HMV) method, and the Walker-Anderson penetration model is used to consider stochastically the cavity expansion resistance of the target material as well as material of projectile and impact conditions. Sensitivity analysis is performed to evaluate the importance of the design parameters on the penetration reliability.
Extended Investigation of the Dwell Effect for an Unconfined Silicon Carbide Ceramic Against Tungsten-Heavy-Alloy Rods
This paper extends a recently published investigation on the dwell capability of single ceramic tiles of limited thickness for protection against tungsten-heavy-alloy (WHA) rod penetrators. Direct impact experiments with long WHA rods against unconfined SiC tiles supported by a steel backing were performed at impact velocities ranging from 1100 m/s to 1800 m/s. The ceramic tile was either bare or had a small buffer layer attached to the front. For the bare ceramic, the area density of the penetrated material Ï increases linearly with increasing impact velocity but at a reduced slope when compared to a semi-infinite RHA target. For the buffered ceramic, dwell is possible up to around 1700 m/s. Compared to the bare ceramic Ï is smaller and the buffered ceramic performs best regarding mass efficiency at an impact velocity of about 1600-1700 m/s before the performance drops sharply towards values in the range of the bare ceramic. Part of the work presented here has recently been published in a journal article [Behner et al., Int. J. Impact Eng. 95 (2016) 54-60].
Effects of Lateral Edges in RHA and Ceramic on the Ballistic Performance against Tungsten Alloy Projectile
The effects of lateral edges in armor materials on the ballistic performance against a long rod projectile were investigated in this study. RHA and silicon carbide ceramic were used in this study. Ballistic tests using a tungsten heavy alloy long rod projectile with a length to diameter ratio of 10.7 were performed to determine the ballistic efficiencies of such specimens. The ballistic efficiencies were also simulated using AUTODYN S/W with the SPH method for a comparison with the experimental results. The experimental results showed that the ballistic efficiency increased with an increase in the distance from the lateral edge of the specimen until the edge distance increased to 6.7 and 2.7 times the diameter of the projectile for the RHA and SiC ceramic specimens, respectively.
Numerical Evaluation of the Feasibility of a Novel Ballistic Helmet Concept
The main goal of this research is to create a new ballistic helmet concept able to defeat high velocity rifle bullets, specifically the 7.62 x 39 M43 round. The current design consists of four layers, where the first layer is responsible for the deformation and breaking up of the projectile, the second layer for stopping the projectile, the third layer for reducing the back face deformation, and the fourth and last layer for absorbing the shock wave send into the helmet shell, next to the back face deflection of the latter. Whereas previous research gave possible solutions for the first three layers, this work focuses on the feasibility of the fourth, shock-absorbing layer. A finite element model approach was used to see the influence of the shock-absorbing layer on the risk on behind-helmet blunt trauma and to determine a suitable standoff based on a maximum force injury criterion.
Ballistic Performance Prediction for SC Jets.
The performance of a shaped charge warhead is usually predicted based on an experimentally determined standoff curve valid for a specific target material. However, with the increased variety of target compositions the traditional “shoot and scoreâ€ approach is not feasible anymore – neither financially nor with respect to time. In this paper, a combined analytical stochastic jet penetration model is presented that permits to predict the penetration process of a shaped charge jet into various target materials. The model combines (semi-) analytical descriptions of jet stretching and breakup with stochastic elements with an extended Walker-Anderson penetration model and an energy-based crater prediction to include the collision of particles with the crater wall.
Simulation Study on Effects of Cap on Armor-Piercing Performance of Nose-Cone-Head Projectile Penetrating Multi-Interval-Layer Steel Target
In order to analyze the effects of cap on the armor-piercing behavior of nose-cone-head projectile (NCHP) and its protective effect on the head of NCHP in the process of penetrating targets, a numerical simulation method was applied to analyze the processes of capped and uncapped NCHP penetrating the steel targets of 4-interval layers with thickness of 10 mm, 20 mm, 10 mm, and 6 mm, respectively, at different impacting speeds from 500 m/s to 800 m/s and target angles of 0° and 30°. The results showed that when penetrating at angle of 0°, the maximum axial overload of the capped projectile was obviously smaller than that of the uncapped one and the attenuation effect of the cap on the maximum axial overload became more obvious with the impacting speed increasing, reaching maximum attenuation of 44.56% at 800 m/s. When penetrating at angle of 30° and impacting speeds from 600 m/s to 800 m/s, the maximum axial overload of the capped projectile was significantly smaller than that of the uncapped projectile, and the attenuation efficiency of the cap on the maximum axial overload increased constantly with the impacting speed increasing. When penetrating at angle of 0°, the effect of the cap on the armor-piercing attitude of the projectile was small. When penetrating at angle of 30°, the capped projectile could keep its better armor-piercing attitude. Especially, at a lower impacting speed, the armor-piercing attitude of the capped projectile was significantly better that that of the uncapped one. Moreover, regardless of the penetrating angle, the mass abrasion of the capped projectile head was smaller than that of the uncapped one, indicating that the cap structure had an evident protective effect on the projectile head.
The Design of the Multi-Layer Hybrid Armor System Using Mg Alloy, Ceramic, and Composite Material for Minimum Weight
To design the armor of the combat vehicle which is not only robust, but also light-weighted is very important for enhancing the survivability of the combat vehicle. This paper suggests the procedure to design the hybrid armor system with minimum weight using Magnesium Alloy. First, a set of armor systems are initially designed by varying combination of materials and thickness. Then these are tested for ballistic limit (V50) by military standard MIL-STD-662F to verify the ability for the bullet proof. Among the armor systems that successfully protected the bullet, the lightest one is selected for further optimization for minimum weight using numerical analysis. For numerical analysis, the model for numerical analysis was developed and verified by matching with experimental results. The results of penetration analysis using numerical analysis are well matched with those of experiment within 3% error rate. The design optimization for minimum weight of the armor system was executed. The results of design optimization for a given threat condition are presented using the contour plot. The design process for the hybrid armor system that uses the initial design, the experiments, the numerical analysis can be used for analysis of vulnerability of combat vehicles.
Study on Lethality Effect of Different Quality of Little Fragment to the Personnel Target
We studied experimentally and computationally the penetration of two little rhombus fragments into a block of ballistic gelatin for developing an improved understanding of the lethality effect to human soft tissues. During the simulation the gelatin is modeled as an isotropic and homogeneous elastic-plastic material. A high speed camera was used to record the process of the fragment penetrated the gelatin block in the experiment. The experimental and stimulant results showed that the maximum diameter of the temporary cavity and the penetration depth are influenced by the mass and velocity of fragment. Furthermore, the time histories of the velocities and displacements have a same law of the 0.15g and 0.25g rhombus fragments, but the time of the temporary cavity expansion and shrink are different by the two different fragments as the same velocity. The agreement between computed results and experimentally measured ones have also been studied.
Research on Kinetic Characteristic and Dynamic Simulation of Direction Controllable Active Electromagnetic Armor
Active electromagnetic (EM) armor comprises detection system, intellectual control system, high pulsed-power supply and EM launcher together. Direction controllable active electromagnetic armor is composed of two flat-plate electromagnetic launchers that placed at a certain angle. Electromagnetic launcher consists of drive coil, insulator, base plate and interceptor. In this paper, the construction of active electromagnetic armor was introduced. Based on the electromagnetism theory and the equivalent circuit equation, the dynamic equation of the direction controllable active electromagnetic armor was established. The relationship between the velocity and the angle of the interceptor and the initial voltage was also analyzed. Based on the conclusions obtained in this paper, the structure of the interceptor was optimized. According to the results of dynamic numerical simulation which is carried out with Ansoft Maxwell software, the EM force acting on the interceptor, the velocity and displacement versus time were obtained.
Study on the Performance of Ceramic Composite Projectile Penetrating into Ceramic Composite Target
In order to study the performance of ceramic composite projectile penetrating into ceramic composite target, the contrast test and numerical simulations of the penetration of standard projectile and the ceramic composite projectile into a ceramic composite target were conducted. The results show that the penetration performance of ceramic composite projectile is obvious superior to that of standard projectile for ceramic composite target. The ceramic nose of ceramic composite projectile fully destroys the ceramic panels anterior to its following armor-piercing projectile body, thus maintaining the penetration ability of the following armor-piercing projectile body.
An Accurate Eulerian Simulation of Shaped-Charger and Explosively Formed Projectile
The Eulerian in-house hydrocode has been tested with two major challenging problems: (1) formation of a shaped-charge, and (2) formation of an explosively-formed projectile. Both of the simulations are compared with our field x-ray test data. The code is based on the three-dimensional explicit finite element method written in C++. For better accuracy, 2nd accuracy throughout the code has been maintained with sophisticated handling of the technique. The predictions using the commercial code has also been compared. Currently our code has shown a relatively good prediction for the EFP simulation. However it is necessary to use an improved material model, especially to isolate the accuracy of the numerical scheme itself.
Effect of Fragment Shape on the Impact Damage of Carbon/Aluminum Laminated Shell Structure
Carbon fiber-reinforced composite materials are widely used in the aerospace area as protective frame against collision. The effect of fragment shape on the impact damage in carbon fiber reinforced aluminum laminates (CRALL) fabricated by carbon fiber reinforced plastic (CFRP) layers combined with aluminum alloy 2024-T3 layers was studied. The 2.48 mm thickness CRALL 2/1 layup and 4.16 mm thickness CRALL 3/2 layup were designed and investigated. The 30 g mass fragments with a flat, hemispherical or conical shape were launched up to 68~238 m/s by the air gun to impact and penetrate these composite targets normally. Experimental results on the 0°/90° CFRP and CRALLs reveal that the fracture modes, ballistic limits and energy absorption are significantly affected by the fragment shape. With the with the increase thickness of CRALLs, the influence of the projectile shapes on fracture modes will be diminished. Due to the strain rate hardening effect, the 4.16 mm thickness CRALL3/2 targets performed higher ballistic limits and better specific energy absorption ability than 4 mm 0°/90° laminated CFRP in all three shapes fragments.
Penetration Mechanisms of Ultrahigh Molecular Weight Polyethylene Fiber Reinforced Laminates by a Conical Projectile Laminated Shell Structure
Ballistic tests were performed on four different-thickness ultrahigh molecular weight polyethylene fiber reinforced laminates (Dyneema® HB26) by a conical-nosed steel projectile. The laminates exhibits much weaker resistance to penetration compared with those impacted by a spherical projectile. Ballistic limit of the laminates increases in the order of thickness: 4, 6, 2 and 8 mm. Fewer than 60% of the fibers that lay within the path of the conical-nosed projectile failed; this was 13.2% ~ 31.1% less than the percent of broken fibers in laminates penetrated by a spherical projectile. It is responsible for poor ballistic performance of the HB26 laminates impacted by the conical-nosed projectile.
Experimental Study on the Penetration Effect of Ceramics Composite Projectile on Ceramic/A3 Steel Compound Targets
In order to improve the penetration performance of projectiles to ceramic composite armor, the nose of 30mm standard projectile is replaced by a toughened ceramic nose, and the armor-piercing performance of ceramic-nose projectile to ceramic/A3 steel composite targets has been experimentally researched. Under the guidance of Impact Dynamics Theory, this article mainly analyzed and compared, under DOP method, the armor-piercing performance between 30mm ceramic-nose projectile and 30mm standard projectile to the ceramic/A3 steel composite targets, especially focusing on the effects made by different nose structures and materials. Under same conditions, a comparative analysis on the aperture and the depth of perforation on the armor plates as well as the residual mass of bullet core has been given. A numerical simulation has been built and computed by ANSYS/LS-DYNA, whose results mainly meet the test results. Combined with the simulation results, further analysis on the penetration performance is given in terms of the residual mass of bullet core. The results show that the ceramic nose has a great effect on the protection of bullet core which lays a foundation for its applying in other warheads.
Numerical Study of High-Density Titanium Alloy Shaped Charge Jet Penetration into Concrete
Numerical simulations for penetration into C35 concrete by 27 kinds of shaped charges with different cone angles, different liner thicknesses at different stand-offs were performed based on AUTODYN-2D software in this paper. Titanium alloy with a density of 6.0g/cm3 was chosen as liner material. The formations of shaped charge jets (SCJs) were studied and the influence rules of liner thickness, cone angle and stand-off on penetration depth and borehole diameter of SCJs were analyzed. Predecessors’ theoretical research achievements were discussed. Results show that large liner thickness is unsuitable for small cone angle, which results in poor penetration efficiency. SCJ formed by larger cone angle and proper liner thickness is not very sensitive to stand-off distance, which has better penetration depth as well as borehole diameter. The penetration depth increases and crater diameter decreases along with the increasing of stand-off distance. These results show a great engineering significance.
Mesoscale and Continuum Modeling of Ballistic Impact on s-2 glass/sc-15 Epoxy Composite Panels
Recently, the authors developed two modeling approaches for composite materials that have been validated against a battery of plain-woven S-2 glass/SC-15 epoxy composite slow-rate mechanical test data. In one approach, a mesoscale mesh was created, and individual yarns, the surrounding matrix, and interfaces were represented using separate simple material models. For the other approach, rules of mixtures were used to relate stresses and strains at the fiber/matrix level to those averaged over the composite as a whole, which allows the composite to be represented by a continuum-level mesh. In this study, both models were used to simulate the ballistic impact of S-2 glass composite panels by two projectiles: a soft M80 ball round and a hard 0.50-cal fragment simulating projectile. Ballistic limits, residual velocities, backface deflections, and delamination areas from the simulations are compared to test data. The relative advantages and disadvantages of the two models are discussed with regard to both accuracy and computational runtime.
Experimental and Numerical Results of High-Speed Penetration of Projectiles with Concrete and Soil
Results of high-speed interaction studies of rigid projectiles with concrete slabs are presented. Experimental and analytical data regarding damage zones and concrete deformation character is presented. The simulations were realized in AUTODYN and used physical-mathematical model of high-speed impact problem, taking into consideration its hardening during dynamic deformation according to Balandin criterion. The simulations represent the process of impact interaction qualitatively and quantitatively correctly, including such process features as crack formation, front and back spall and damage of concrete and forming a cavity in the sand.
The Development of a Bullet Simulating Projectile for Body Armor Testing
The standardized ballistic testing methodologies for Personal Protective Equipment that are currently used, incorporate the use of common mass production projectiles. The discrepancies in their attributes, material composition, geometry, assembly, production tolerances, introduce extra variability in their responses, for the stochastic physical phenomenon, that is ballistic impact. A prototype of a Bullet Simulating Projectile (BSP) was developed for replacing commercial 9mm projectiles, strongly limiting the unknown variables that normally manifest themselves in ballistic impact tests. The effectiveness of the proposed BSP design was examined against soft protection targets in terms of penetrability and induced behind armor blunt trauma (BABT). The proposed BSP design was used versus multilayered non-crimp aramid fabric packs backed against Weible red plastilina. The resistance to perforation and the BABT were measured and compared with commercial 9mm projectiles. A finite element model was developed for investigating the local response of multilayered non-crimp aramid fabrics against the 9mm Parabellum projectile and the BSP. The fabric is presented as a dual ±45o angle-ply yarn based model with its yarns being interconnected using cohesive formulation elements. The results were compared with the experimental data.
Numerical Investigations on Ricochet of a Spinstabilised Projectile on Differently Shaped Target Surfaces
Conflict and large-scale disasters are more likely to occur where large populations reside. Expanding urbanisation will see future peace-keeping missions in such closed urban locations where foot soldiers find themselves surrounded by house walls and close to their armoured vehicles. In closed environments, the likelihood of projectile ricochet arises in the event of combat. It is crucial to fully understand the interaction of different parameters during projectile ricochet, and continuously improving FE-codes can give a closer insight on the ricochet scenario. This investigation focuses on the target shape upon oblique impact, and its influence on projectile ricochet is experimentally and numerically investigated. Numerical simulations—using the explicit Lagrangian solver in the commercial LSDYNA software—are used for a qualitative investigation, as measurement precision limits determination of the influence of shaped surfaces on ricochet.
The Influence of Edge Effects on the Ballistic Performance of Transparent Armor
Edge effects may cause reduced ballistic performance close to the edge of armoring parts. When a ballistic test of an armor sample is performed, it is important to define whether this test is aimed to the main area (MA) of the sample or to the structurally weak areas (SWA) near its edges. Some standards define excluded zone (EZ) to avoid test within SWA, but for transparent armor (TA) the available data regarding the extent of the SWA is rather limited, resulting in possibly insufficient EZ. In this work, typical TA samples were tested against Kinetic Energy (KE) and Fragment Simulating Projectile (FSP) threats, at both MA and edge related SWA, and the differences in the ballistic performance were examined. The obtained results suggest that the edge effect extends to at least 100-150 mm from the edges. Finally, we recommend that for ballistic performance purposes, explicit definitions of sample size, impact location and shooting sequence, should be considered to be incorporated into ballistic standards to ensure repeatability of the tests.
Development and Application of Model for Adobe to Penetration in Adobe Targets
Adobe materials are becoming more prevalent on the battlefield and so it is necessary to be able to assess their ballistic performance to a range of threats. The aim of the work described in this paper was to develop a material model that is capable of predicting the ballistic response of the adobe material within the spread of experimental data. The model is generated by a combination of theoretical and semi-empirical techniques and triaxial testing is used to determine the constitutive response. The simulations demonstrated the sensitivity of the adobe’s shear and compressive meridian to the prediction of penetration depth and demonstrated that the compressive meridian was the dominant process. The simulations have also been compared with shaped charge penetration experiments with good agreement for the borehole shape and perforation time. The paper discusses the aspects of the model that require further development to predict the cratering response.
Estimation of the Bullet Depth of Penetration based on the Numerical Integration of Stochastic Differential Equation
The ballistic performance of materials subjected to projectile impact loading is analyzed based on the determination of the ballistic limit velocity (BLV) or the depth of penetration (DoP). The ballistic assessment of thick plates is generally based on the use of the DoP parameter. Experimental observation reveals the randomness of the DoP of a given projectile penetrating the target material at a given impact velocity. This contribution models the projectile DoP using the Brownian motion approach. The key advantage of the developed model is that it supplies insights about the statistical distribution of the DoP instead of only providing an analytical estimation of this parameter. Furthermore, if perforation starts to occur, this approach might also yield information about the residual velocity and its dispersion. Finally, the model results are compared with the ones produced by the most existing methods.
Penetration Performance of Ultrafine-Grained Copper Shaped Charge Liner
It is known that the fine grain size of a copper shaped charge liner improves penetration performance. To obtain fine microstructure in copper, recrystallization after plastic deformation is usually used. In this study, ultrafine grain of copper was obtained by a severe plastic deformation technique called equal channel angular pressing (ECAP). Conical liners were fabricated from ECAP processed billets. Mechanical properties and penetration performances of ultrafine-grained copper shaped charge liners have been compared with those of conventionally forged and recrystallized ones.
Medium-Weight Combat Vehicles Mine Protection Development Methodology
In modern warfare, ballistic armor and especially underbelly protection is one of the critical considerations in the design of an armored personnel vehicle. The development of underbelly protection is complex, expensive, time consuming and therefore needs to rely mostly on numerical simulations. This kind of critical and life-saving capability must eventually be validated through blast tests. The practice of developing an underbelly protection is even more challenging when developed for a medium-weight vehicle - where the weight of the vehicle is limited. When the development is under strict time and budget constraints, one had to come up with a unique approach of developing an underbelly protection using numerical analysis combined with small-scaled experiments. This approach has already been used and proven effective during the development of previous heavy platform, and needed even more when the vehicle is limited by its weight. This paper describes the methodology used by the Israeli Ministry Of Defense for the development of a new medium-weight, wheeled vehicle underbelly protection. This unique approach can be described by the following iterative steps: (1) Initial concepts Design, (2) Numerical analysis, (3) Small scale tests, (4) Design improvements, (5) Small scale blast test of vehicle's structure and finally (5) Full scale vehicle mine blast experiment. The first step of initial design includes various geometric solutions, all of the same weight. Step 2 (Numerical analysis) narrows down the number of concepts to a maximum of three options to be validated in small scale experiments. This paper presents the methodology of the series of simulations performed with LSDYNA as well as the set-up and preparations of the small scaled tests. When keeping the scaling principles, the results of the small scale experiments showed good structural behavior correlation between the experiments and the numeric analysis. Moreover, it also emphasized the same advantage to the chosen solution. The conclusion from the study so far is that the method of using small scale experiments, combined with finite elements numerical analysis, is beneficial. It saves time and costs of the medium-weight vehicles development process – as a step towards the final approval of the full scale prototype.
Protection Capabilities of HHA and UHA Steels against Long-Rod Kinetic Energy Penetrators
The protective capabilities of three different armor steels of the HHA and UHA class against a long rod penetrator (LRP) were examined. Due to the lack of commercial availability of thick armor plates, the specific ballistic behavior under overmatch conditions, and unavoidable experimental scatter, we were unable to confirm any performance differences among the steels in ballistic testing, even when compared to standard RHA. In a second approach, numerical simulations of the ballistic behavior of the armor steels based on material testing (tensile tests and planar-plate-impact tests) were performed. The simulations provided the possibility to examine the steels in unavailable configurations, i.e. thickness. With this combined approach it could be shown that UHA steels may give a considerable protection increase against LRP in diminishing their maximum effective range by at least several hundred meters compared to HHA steel.
Three types of porous raw particle materials based on expanded glass, ceramics and polymeric microspheres in combination with polymeric binder were used to design a new type of blast wave energy absorber. The effect of binder amount and type of filler on the static and dynamic properties of designed materials was evaluated. The developed material was used as the interlayer of blast resistant litter bin. Series of experiments of the response of given litter bin to TNT explosive charges of different weight (up to 3 kg) were performed. Numerical simulation of the experiments was performed using of LS DYNA finite element code. The detonation of 3 kg TNT did not cause any fracture of the outer steel layer. This conclusion has been verified for different position of the TNT charge. Good agreement was concluded between the results of the blast experiments and numerical simulations.
Reactive Panels with Non-Metallic Cover Plates
A study on how to perform reliable numerical simulations of the interaction between shaped charge jets and ERA-panels with non-metallic cover plates has been carried out in order to facilitate further studies on how panels with non-metallic cover plates can be used in ballistic protection designs. As reference for the simulations, a series of experiments have been performed with alumina (Al2O3), silicon carbide (SiC), boron carbide (B4C), glass fiber reinforced plastic (GRP) and steel in the cover plates. Simulations comparable to the experimental cases were performed in LS-DYNA, where available material models and appropriate numerical formulations for the materials in this application were evaluated. A Lagrange-SPH approach and the JH-2 material model were found to be useful for the ceramics, while the GRP was modelled in Lagrange with a custom implemented material model. Each ply in the GRP was assigned as a separate part to accommodate for the variation in the anisotropic structure. The numerical simulations reproduce the behavior for the flyer plates and effect on the shaped charge jet found in the experiments.
Parametric Design of a Muzzle Brake by Computational Fluid Dynamics to Reduce Crew Noise Exposure During Training
A programme of work was undertaken to redesign the L118 105mm Light Gun muzzle brake to offer a potential solution for reducing the firing impulse noise (FIN) experienced by the gun detachment whilst operating the platform during training exercises. The key drivers for this study were compliance with the UK authority on the Control of Noise at Work Regulations 2005 whilst maintaining minimal effect on the platform from a reduction in the muzzle brake efficiency. On completion of this study two muzzle brake designs were presented that could potentially reduce the FIN level experienced by the gun detachment. These designs were recommended for further study and have since been taken forward for prototyping and field testing during 2016.
Experimentation using Hot and Cold Steel Plate Targets Against 7.62mm Ammunition.
Recent background research highlighted that data was limited into the characterisation of low carbon steels at hot and cold temperatures against 7.62mm Ball and Armour Piercing (AP) ammunition. However, available data indicates that the strength of steel plates increases with decreasing temperature. This paper looks further at this phenomenon with Hot and Cold targets that were environmentally conditioned at the specific temperature for 24 hours, prior to ballistic evaluation. The steels used were DH36, S275 and S355 and the target temperatures were Hot (>+50°C), Ambient (~12°C) and Cold (<-20°C). The target plates were 10mm thick. All shots were 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.
A Preliminary Study in the Variables of Thoracic Ballistic Trauma
The terminal behaviour and trauma produced by penetrating projectiles is known to depend on the mechanical and physical properties of the tissue. Impact with bone is thought to cause injuries of greater severity due to a potential increase in bullet instability, deformation and/or fragmentation. The interaction of flat bones like the ribs and the effect of the rib cage in thoracic ballistic trauma remain unclear. The aim of the study was to determine the effect of ribs on the terminal behaviour of penetrating projectiles and the resulting trauma produced via a gelatin-based model. Three sample groups were compared: (i) plain gelatin, (ii) rib-embedded gelatin with direct rib impact, and (iii) rib-embedded gelatin with intercostal muscle penetration (between ribs). Two projectile calibers (5.56 mm and 7.62 mm) and two impact velocities (for 5.56 mm) were evaluated. The influence of ribs on the terminal effects of penetrating projectiles appears to be minimal.
Ballistic Performance of Reground Resin in Extruded Polycarbonate Plates
Polycarbonate is a suitable engineering material for applications where safety, protection, and transparency are required. One such application is transparent armor in which polycarbonate is often used as a spall shield. The ability of the polycarbonate to deform is key to its effective use as a spall shield in optically transparent armors, however the performance is not always consistent. In practice of producing polycarbonate sheet, portions of the sheet that are not suitable for use can be reprocessed along with virgin material into usable plate. The reprocessed content was believed to be a possible contributor to variable ballistic performance of laminated armors. Grades of polycarbonate with differing levels of reprocessed material were ballistically tested with the 0.22 caliber fragment simulating projectile at high, room, and low temperatures. No significant difference in ballistic performance, consistency, or failure response was observed.
A Note on the Dynamic Spherical Cavity Expansion of Concrete with Liquid Constitutive Model
High pressure is applied to concrete target by the projectile in hypervelocity penetration. Moreover, concrete material which undergoes large deformation is incompressible and can be depicted by liquid constitutive model. The present work modifies the cavity expansion theory by characterizing the incompressibility with Bingham liquid constitutive model considering the viscosity of the incompressible material according to Cleja-Tigoiu’s work. The analytic expression for the relationship between the pressure on the cavity boundary and the velocity of the cavity expansion is derived in this paper. Then, the effects of material parameters in the modified model are studied, which is the basis of the calculation of the drag force in hypervelocity penetration. At last, some penetration depth results of long rod impact concrete target on hypervelocity are predicted based on the modified model, which are in good agreement with the experiments.
Aluminium Block against Oblique Penetration of Tungsten Alloy Long Rod
This paper studied ballistic performance of aluminium blocks subjected to oblique impact of tungsten long-rod projectiles. Penetration experiments of tungsten alloy long rods impacting 25.4mm thick blocks made of aluminium 7075-T651 were conducted at a nominal velocity of 1.25 km/s under NATO 60 degrees obliquity. A witness plate made of steel was placed behind the target with an air gap of 300mm. Flash X-ray radiography was applied to capture images of the projectiles before and after penetration. The test results showed the effect of the thick aluminium block to deflect the long rod projectile from its line of flight. Numerical simulation of the experiment was carried out by using the hydrocode LS-DYNA to explore defeat mechanisms of inclined aluminium blocks against tungsten long-rod projectiles. The inclined aluminium block created the upwards mushrooming and bending of the projectile’s nose during the whole process of penetration. The effect of trajectory deviation was insignificant during and immediate after the penetration; however, it became significant after some time of the penetration, resulting in a noticeable increase of the pitch angle of the residual projectile. Consequently, the residual projectile ricocheted from the surface of the witness plate with limited penetration.
The 9x19 mm Ammunition Rebound Phenomenon
This article is a summary of the first phase of 9x19mm ammunition exploration after the impact. The study included setting the limit of the ammunition ripping angle after hitting the metal barrier. To do the test was used doppler ballistic set, ballistic soap and ballistic gel. The paper is concluded with results analysis that can be used for future work.
Transferring a Hydrocode based Blast Wave Propagation to an Automotive Industry Standard Finite Element Code to Simulate Non-Military Armored Vehicles
This paper outlines the transfer of a hydrocode based blast wave propagation caused by a detonation to a finite element code used for crash simulation in the automobile industry. With a combination of two simulation processes, the identification of weak points in armored vehicles construction as well as the dimensioning of armor plates can be audited in a very early development stage. The authors evince cost and time benefits resulting of multiphysics interaction of different codes in the development of non-military armored vehicles at BMW Group speeding up R&D and reducing the requirement of cost intensive prototypes. This results in a fast and convenient R&D process on manufacturer side, while providing higher quality products on customer side.
Numerical Simulation of Penetration Resistance of Ceramic Composite Target.
The numerical simulation of penetrating the ceramic composite targets was carried out by using the nonlinear dynamic software AUTODYN-2D and the SPH-Lagrange model. The deformation process of the composite target and the residual velocity of the projectile were studied. The protective performance of ceramic composite targets with structural steel, armored steel and aluminum alloy as backplane materials were analyzed respectively. The effect of initial velocity variation on the anti-penetration performance of aluminum alloy backplane ceramic composite target was studied. The effect of thickness configuration on the penetration resistance of the composite target was also analyzed in the condition of the same areal density. The results show that the residual velocity is the smallest when the aluminum alloy is used as the backplane material. The residual velocity of the projectile is linearly related to the initial velocity. When the areal density is the same, the thickness configuration affects the protective properties of the composite target. Therefore, the anti-penetration ability of the ceramic composite target can be changed by altering the backplane material and the thickness configuration. This conclusion provides a strong reference for composite target design.
Modeling the Effect of Initial Disturbances when a Bullet Impact in Gelatin
Impact experiments with gelatin targets often lack information on the pitch rate of the bullet at the time of impact. Usually, this boundary condition is also ignored in numerical modelling. To investigate the effect of pitch rate on the bullets behavior in gelatin, a numerical study is performed for various impact angles and pitch rates. To enable this study, a constitutive model describing the hyperelastic, nearly incompressible and viscoelastic behavior of gelatin is implemented in a commercial finite element code. We investigate how the pitch rate and impact angle affects the depth where a full metal jacket bullet starts to tumble in a gelatin target. Results indicate that whilst the impact angle dominates the bulletgelatin interaction, large pitch rates (>150 rad/s) should be included in any analysis. However, in most ballistic experiments the pitch rate is low (<70 rad/s) and its effect can largely be ignored in simulations or analysis.
A Potential Methodology for Evaluating Ceramic Quality.
Metal armor alloys have well-established, stand-alone, ballistic acceptance criteria to demonstrate consistent lot-to-lot performance, thus allowing metals to be qualified prior to cutting and forming into the final armor design. By contrast, ceramics do not have standalone quality assurance criteria. ARL undertook a small-scale effort to evaluate an energybased assessment methodology for bare ceramics developed by TNO in the Netherlands. Bare sintered aluminum oxide tiles and hot-pressed silicon carbide tiles were evaluated using the energy methodology. While this method may have promise, a number of issues must be overcome before this method can be adopted to determine ceramic quality.
Experimental Round Robin for Predicting Electronic Component Response from High-G Loads
The Air Force Research Laboratory led an experimental Round Robin with members of the Department of Defense and Department of Energy to validate capabilities to predict the response of electrical assemblies due to mechanical shock. Specifically, high-g shock that has peak accelerations in the 10,000–20,000 g range with durations of 0.1–0.5 ms. These accelerations were generated through the use of a Very High-G machine and a MTS Drop Tower. The test article contained an array of accelerometers placed on each of the four printed circuit boards within the unit. Input data was collected for the computational performers by mounting accelerometers to the top and bottom of a test fixture while simultaneously capturing the response of the item under test inside of the fixture. The input data was provided to the different performers, then the performers’ prediction results of the test article's accelerometer data were compared to the experimental data. This paper will present the experimental techniques that were utilized for the MTS Drop Tower series, the input data, and a discussion of the evaluation metrics used for the comparison of the models to the experimental data.
Damage Effect and Parametric Sensitivity Research of Different Aggregate Composite Target Subjected to Projectile Penetration
In order to study the damage effect of aggregate composite target, a 3D microscopic numerical model of composite material which was composed by randomly embedded metallic particle, mortar as well as their adhesive transition layer has been built up by using the specific meso-structure characteristic of composite target and background grid method. On this basis, the meso-scale numerical simulation has been performed to the process of projectile penetration to composite target by using dynamic finite element method. Meanwhile the orthogonal testing method has been adapted specially to making statistic analysis about the influence of three parameters—impact velocity, aggregate strength and aggregate modulus to penetration damage effect. The major parameters and the relationship of parametric sensitivity related to damage effect have been primarily concluded. The results are capable to provide technical support for damage assessment of penetration trajectory deviation, energy loss as well as the design of penetrator warhead.
A Consistent Framework for the Assessment of Angled Penetration
Recent studies have identified routes to modularizing projectile penetration calculations. These, along with work to derive factors for behaviours such as nose erosion and wake separation, make a uniform modular penetration framework for the PALETTE terminal effects code desirable. This paper presents a modular approach, based on the Differential Area Force Law (DAFL) approach. In order to incorporate empirically based historical penetration routines a transform to a DAFL resistance function is required. Using this approach a conical nose penetration relation has been transformed and tested, showing results within 0.034% of the original model. This enables the transformed empirical relation to be used in DAFL analyses considering impact angles with respect to both the surface and velocity vector (which result in curved trajectories). We have also introduced an automated approach for the selection of appropriate models, which will form part of the PALETTE modular penetration approach in future versions.
The paper deals with study of the concept and design of the solid propellant Divert and attitude control (DACS) system. The Solid Propellant Divert and Attitude Control systems, which provides pitch, yaw and roll control and divert propulsion for the kill vehicle maneuvering, these thrusters uses variable throat are through Valve controls to modulate the thrust & also thrust vectoring. The four divert thrusters provide short/ long pulses to quickly and accurately position the interceptors. The critically of the solid propellant motor design and the thrust modulation using the throat area have been studied. Design has been carried for the hardware of motor, the valves, and the nozzle throats. The design involves selection of materials for motor, divert thrusters and the igniter. Initial ballistics performance predication has been carried out for propellant grain design to meet the requirement for the thrust modulations and the continuous attitude control system.
Material Characterization of Ballistic Roma Plastilina No. 1 Clay.
Compression tests were conducted for Roma Plastilina No.1 (RP #1) to characterize the material responses as functions of temperatures and loading rates. Due to barreling of the specimen, the measured stress-strain curves were not representative of the material stress-strain curve. Numerical analysis was carried out to understand the barreling effects and correlate the measured stress-strain curves and material response. A parametric study was then conducted to find a set of material parameters accounting for strain rate, temperature and tensile properties (different from compression properties) to best match the impact and drop tests.
Ballistic Impact of 5.56 mm Small Arms Projectiles on Steel
This paper presents experimental and 3-D numerical simulation of ballistic impact of 5.56 mm projectiles on steel plates. Standard 5.56-mm projectile comprising Cu-Ni as outer jacket and three different inner cores namely, steel-lead, Aluminum-lead & full lead at an impact velocity of 900 m/s is considered for analysis. Target plates thicknesses 1, 3.5 mm for steel at angle of obliquity of 0° has been considered in experimentation. The residual velocity curves were constructed and compared. All necessary material properties have been taken from published literature and numerical simulations have been performed using explicit commercial code ANSYS-AUTODYN. Constitutive models play a key role in simulation of impact events, rate dependent continuum damage models have been employed for both projectile & target. The findings of numerical investigations compared with experimental results. A good agreement found between computed and experimental results in terms of exit velocity, size & shape of perforation. A relative assessment of damage potential of three projectiles is also made.
Research on Dynamic Mechanical Behavior of Silicon Rubber Under Different Temperatures
By use of split Hopkinson pressure bars(SHPB) technique with temperature controllers, a kind of silicon rubber is investigated for understanding its dynamic constitutive behaviors at high strain rates (740-1740s-1) and different temperatures (-40℃, 20℃, 80℃). Experimental results show that silicon rubber is strain-rate sensitive and shows viscoelastic characteristics at room temperature. Moreover this kind of silicon rubber is temperature sensitive at the same strain rate, but is not strain-rate sensitive at high or low temperature.
Method for Non-Destructive Characterization of Projectiles and Cartridge Cases
A proof of concept non-destructive test system has been designed and tested that is capable of characterizing both Cartridge Cases and projectiles, both intact as well as those discharged from a weapon. The technique utilizes a device equipped with a proprietary and patented sensor which detects energy reflected off the unit under test. This detected signal undergoes Fourier Transformation which creates a signature which can them be used for comparison with other existing samples for matching purposes. This system has been shown to be able to match Cartridge Cases as well as projectiles to a degree that could potentially allow matching of samples to a degree sufficient to determine like production lot members, and other linked criteria. This is system is projected to be much more cost effective than current systems and the hope is to have units installed in Forensic vehicles and laboratories nationwide, and globally for government and law enforcement applications. By standardizing the measurement system, data can be stored in a repository similar to current repositories, for remote access to stored data as well as to be able to upload measured signatures directly to the data base. The system has shown good results in early tests and is ready to progress through further testing to a preproduction stage, once funding has been secured to enable this.
Delay Compensation in HILS of Aerospace Systems
Embedded systems of Aerospace vehicles can be developed and evaluated 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. We can add the complexity of the plant under control to the test platform by adding mathematical models of all related dynamic systems. The set of all these mathematical models are known as “simulated plant’’. The other emulated systems will be as interfaces between the Simulated plant and the Embedded system. The emulated systems will be excited by the Simulated plant and their response will be given to Embedded system under test. All these systems in the HILS testbed causes considerable delay. To compensate for this delay, different methods were proposed earlier. This paper describes those methods and suggests suitable method to be implemented.
Fast-Running Model Enhancements for Predicting Damage Scenes from Synergistic Effects of Multiple Penetrator Impacts
The present work modifies the Walker-Anderson model in order to accurately compute damage scenes due to synergistic effects of multiple penetrators. Modifications are proposed to the model governing equations in order to account for differences in the target strain rate field and already damaged surfaces as a result of the action of multiple penetrators impacting in close spatial and temporal proximity. The damage scenes predicted by the fast-running model are then compared to those predicted by a range of high-fidelity computational phenomenology simulations to assess the model’s performance.
Influence of Thickness/Diameter Ratio on Strain Hardening Behavior of High Molecular Weight Polyethylene after Dynamical Compressive Tests using Hopkinson Pressure Bar
Ultra-high molecular weight polyethylene samples were submitted to dynamical compressive test in a split Hopkinson Pressure Bar. Three thickness/diameter ratio (0.11, 0.44 and 0.64) and two strain rates (3250 s-1 and 6500 s-1) were used to understand how the test set-up influences the stress equilibrium and the constancy of strain rate during the impact. Concepts of stress equilibrium, constancy of strain rate, dynamical stressstrain curves and dynamical mechanical properties of the material were evaluated. All studied samples achieved stress equilibrium, but the samples with smaller ratio achieved it more easily. Nevertheless, samples with the smallest ratio were not able to achieve strain rate constancy. Additionally, dynamical stress-strain curves were plotted to investigate the mechanical properties of this material at high strain rates. T-tests pointed out that the properties are controlled by the strain rate rather than by the specimen’s thickness/diameter ratio.
Predicting the Rupture of Composite Plates following a Hypervelocity Impact
Most spacecraft have at least one pressurized vessel on board. For robotic spacecraft, it is usually a liquid propellant tank. In some satellite or spacecraft designs, the fuel tank or some other pressurized vessel is necessarily exposed to the hazards of space, including the micro-meteoroid and orbital debris (MMOD) environment. Because of the potential of serious mission-threatening damage that might result following an on-orbit MMOD impact, a primary design consideration of such spacecraft is the anticipation and mitigation of the possible damage that might occur in the event of such an impact. While considerable energy and effort has been expended in the study of the response of non-pressurized spacecraft components to MMOD impacts, technical and safety challenges have limited the number of tests that have been conducted on pressurized elements of such spacecraft. As a result, several investigators have taken to modelling pressurized vessels as flat plates under uniaxial or bi-axial tensile loading conditions. This paper presents the development of a data-driven equation for initially stressed flat composite material plates that differentiates between impact conditions which, given a plate perforation, would result in only a hole or crack from those which would cause catastrophic plate failure / rupture. If this equation were subsequently shown to also model the rupture/no-rupture behavior of actual COPVs, then it could also be used to appropriately tailor the design parameters and/or operating conditions of a pressurized tank. Tank designs could be adjusted so that if that tank were to be struck and perforated by the impact of an MMOD particle, then only a hole would occur and additional sizable debris would not be created as a result of that impact.
Numerical Analysis of Ceramic Composite Armour Subjected to Ballistic Impact
A numerical investigation is presented in this work to study the ballistic performance of Aluminum Oxide (Al203) ceramic plates bonded to a polycarbonate backing subjected to impacts from 7.62 mm diameter calibre projectiles. The ceramic plate measured 102×102 mm with a thickness of 5.8 mm. A numerical model was 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 materials and backing material, respectively. The residual velocity and depth of penetration (DoP) into the backing material was obtained and compared with the available experimental data. The results showed that when the ceramic plates were impacted by a projectile, damage mechanism of the fragmented ceramic included radial and circumferential crack lines along with a pulverized center and a highly eroded bullet.