Gun Launch Research Articles

A refined prediction model for the initial disturbances of the projectile in the self-propelled gun

Abstract In the gun launch process, the continuous propellant combustion provides power and energy for the projectile. Due to the gap between the projectile and barrel, the high-speed motion of the former is generally accompanied by contact and collision with the latter. Meanwhile, the gun also recoils under the propellant gas. Notably, the above complex motion of the system causes the initial disturbances of the projectile and muzzle. Previous launch dynamic models usually neglect the influence of the gun recoil on the combustion and flow in the chamber. However, the gun recoil inevitably further increases the chamber’s free space, resulting in the calculation deviations of projectile and muzzle disturbances. The above deviations ultimately determine the firing accuracy and firing stability prediction. To study the in-bore projectile motion and subsequent external ballistic process more accurately, an improved coupled calculation method of launch dynamics is developed. This work combines the interior ballistic two-phase flow dynamics considering the gun recoil, in-bore projectile motion theory, multibody system dynamics, and necessary high-precision numerical schemes. The launch process of the 155 mm self-propelled gun is studied. As the results show, the calculated vibration characteristics, dynamic response, and interior ballistic performance indexes are consistent with measured ones, verifying the feasibility of the above method. In addition, the initial disturbances of the projectile with and without considering the recoil’s influence on the combustion and flow in the chamber is discussed. The work in this paper provides an accurate tool to predict the initial disturbances of the projectile.

Study on the Influence of Combustible Cartridge Force of Propellant on the Pressure Wave of Modular Charge

Abstract In order to study the influence of the change of force of propellant of combustible cartridge case on the interior ballistic performance of gun, the combustion performance tests of four combustible cartridge case formulations were carried out, and the pressure-time curve of actual combustion process was obtained. On this basis, the combustion law of combustible cartridge cases with different force of propellant is obtained, and the combustion law is introduced into the two-phase flow simulation model of modular charge, and the influence law of combustible cartridge case force of propellant change on the pressure wave in the interior ballistic process of gun launching module charge is obtained by simulation. The research results have certain reference value for improving the design of combustible cartridge case with large-caliber modular charge.

Research on Electromagnetic Protection Characteristics of Vehicle-mounted Electromagnetic Railgun Launcher Lifetime Counting Device

When the vehicle-mounted electromagnetic gun is launched, the vehicle body is subjected to strong arc reaction, magnetic field interference and shock wave phenomenon. By establishing the external magnetic field model of the multi-tube launch chamber, the electromagnetic protection characteristics of the vehicle-mounted electromagnetic gun launcher’s full-life counting device are studied, and the magnetic field characteristics during launch are analyzed by COMSOL software, and the distribution position of the counting device is selected. Then, based on the electromagnetic shielding technology, conduct anti-interference technology research on the counting device, adopt the method of combined shielding, compare and analyze the shielding effectiveness of each shielding body, and propose the best shielding scheme. The life counting device works safely and normally. Therefore, the research method in this paper can provide an electromagnetic shielding scheme for the anti-jamming technology of the remaining electronic equipment of the vehicle-mounted electromagnetic gun, and can provide guidance for the design of the vehicle-mounted multi-barrel electromagnetic gun launching system.

Experimental study on dynamic mechanical properties of projectile 155mm ERFB BT material

Artillery projectile 155mm high explosive (HE) extended range full bore boat tail (ERFB BT) and its components experience a high pressure loading of the propellant during gun launch. Mechanical properties of an engineering material are measured using quasi-static tensile test at room temperature. The materials of the projectile and its components are expected to survive time dependent propellant pressure loading inside the gun, which lasts for few microseconds. To investigate dynamic mechanical properties of the projectile and its components at medium strain rates and elevated temperature, the experimental analysis is undertaken. This research paper aims to examine the effect of medium strain rates and elevated temperatures on flow properties of the materials used in the projectile. The uniaxial tensile tests at the medium strain rates between 0.01 s-1 to 1s-1 and at elevated temperatures ranging between 150°C to 500°C are performed separately. The Considѐre criterion was applied to evaluate strain hardening exponent of the materials. Values of strain hardening exponents of shell body and boat tail materials are less than that of driving band material. Strain rate sensitivity of the materials is observed to be very low, thus indicating a good resistance to plastic deformation. The yield strength and true yield strength of the materials fall with increase in temperature.
 

Research on the sealed launching technology of underwater gun

With the progress of military technology, the underwater combat capability of the world’s major naval powers has developed rapidly. In order to effectively deal with the underwater threat, the related technology research of underwater gun is carried out based on supercavitation technology. Due to the particularity of underwater launch environment, the research of underwater gun launch technology still faces many problems. In this paper, the sealed launching technology of underwater gun is taken as the research object. By comparing with submerged launching and air curtain launching, the advantages of sealed launching technology of underwater gun are analyzed, and the muzzle sealing technology, sealed launching interior ballistic technology and continuous stable water entry technology of underwater gun are preliminarily studied. Opinions and suggestions are put forward for related technologies, which can provide reference for underwater gun launch technology research and engineering practice in the future.

Plastic Deformation of High Explosive Projectile 155 mm during Gun Launch Conditions using Finite Element Method

The structural integrity of artillery projectile 155mm high explosive Extended Range Full Bore (ERFB)boat tail designed for 155mm howitzer guns of 39, 45 and 52 calibre plays a key role inside the gun barrel. Thisprojectile comprises a shell body, a driving band, a boat tail, nubs, an explosive, and a fuze. Plastic deformationof the projectile and stripping of driving band are not permitted, when projectile is fired. An investigational study is necessitated to check the plastic deformation of the projectile subjected to maximum propellant charge pressure.The aim of this study is to check the effective plastic deformation and affirm the structural integrity. A 3-D explicit dynamic structural analysis of 155 mm HE ERFB BT during gun launch conditions is carried out by finite element method using FE code ABAQUS/Explicit. To understand the non-linear mechanical behavior of the projectile, the true stress-strain curves of the materials are considered. The plastic behavior of the projectile subjected to the time-dependent loading is studied by using the von Mises plasticity model. The results reveal that the shell body and boat tail have no plastic deformation and the most stressed component is the driving band. The investigation has affirmed the structural integrity of the projectile during gun launch conditions.

Analysis about Change of the Armature's Average Speed for an Experimental Rail Launcher

In this paper, we measured the armature velocity of an experimental electromagnetic launcher by B‐dot method and analyzed the change of the armature's average speed. The electromagnetic gun launching process was also simulated by Ansoft Maxwell simulation software. The launch current is used as the model's excitation which means that the current in the model is the same as the rail current. Ansoft Maxwell's 3D model can accurately simulate the launching process, in theory. We found that there was an unexpected rise during the real launching process. The phenomenon can be discovered in the following several experiments. We analyzed several possible causes such as the inductive gradient change, rail broken and inaccurate measurement of B‐dot probe. The inductive gradient is an important parameter in the launching process and can affect the armature speed. After checking the measurement problem, we also found that the wave form of the output signal from the probe where the unexpected change occurred was normal but the amplitude was very small. The measurement method was proved correct. The rise of average inductance gradient leads to the unexpected increase in average speed and the small signal. Furthermore, the physical reason for the change of inductance gradient should be the change of current distribution. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Experimental Research on Igniting the Aviation Kerosene by W-Zr Reactive Fragment

Taking W-Zr reactive fragment as the research object, the influence of fragment density, shape and size parameters on the armor-piercing ignition fuel tank was studied through the simulated target test of 12.7mm ballistic gun launch. Combined with high-speed camera, the armor-piercing ignition behavior of the reactive fragment and ignition mechanism were revealed. The results show that the ignition fuel tank with low and medium density activity fragments has better effect, and the ignition speed of the fragments with high density decreases about 26%. The cube shape fragments have the best ignition performance, followed by cylindrical fragments and spherical fragments. The ignition ability of 7mm and 8mm fragments is equivalent, while the ignition ability of 8mm fragments is slightly stronger. The ability of W-Zr fragment to ignite aviation kerosene is closely related to the content of active components and the degree of breakage when it hits the target plate. Under the action of high-speed impact on the target plate, the fragments ware quickly broken into fragments with a certain flying Angle and high temperature combustion. Under the coupling action of the impact kinetic energy of the fragments and the chemical reaction heat, the critical ignition condition of fuel is reached, and the fuel tank is ignited.

Modeling, Simulation and Uncertain Optimization of the Gun Engraving System

The system designed to accomplish the engraving process of a rotating band projectile is called the gun engraving system. To obtain higher performance, the optimal design of the size parameters of the gun engraving system was carried out. First, a fluid–solid coupling computational model of the gun engraving system was built and validated by the gun launch experiment. Subsequently, three mathematic variable values, like performance evaluation indexes, were obtained. Second, a sensitivity analysis was performed, and four high-influence size parameters were selected as design variables. Finally, an optimization model based on the affine arithmetic was set up and solved, and then the optimized intervals of performance evaluation indexes were obtained. After the optimal design, the percent decrease of the maximum engraving resistance force ranged from 6.34% to 18.24%; the percent decrease of the maximum propellant gas temperature ranged from 1.91% to 7.45%; the percent increase of minimum pressure wave of the propellant gas ranged from 0.12% to 0.36%.

An initial velocity model study of electromagnetic railgun based on back propagation neural network

The velocity of launch has been the key factor restricting the application of electromagnetic rail. For electromagnetic launch system, the structural parameters change directly or indirectly affect the Launching velocity of the electromagnetic launch system. In order to improve the initial velocity of the electromagnetic railgun. The mathematical model of electromagnetic rail gun launch was set up, the structure parameters of armature and the size of the pretension force between armature and orbital were variables, based on the target function, The equivalent model of rail gun BP neural network is established by using the calculation results of mathematical model, and the model of rail gun BP neural network was optimized by electromagnetic emission test data. The error of rail gun BP neural network model optimized by experimental data is 18.5% lower than that before optimization and 6.5% lower than that of experimental data. The results show that the launch speed of the optimized rail gun BP neural network model is closer to the actual speed.

Model updating of gun recoil mechanism based on time domain response

For gun launching dynamics modeling, the accuracy of the recoil and counterrecoil model is important. In order to improve the accuracy of gun recoil mechanism modeling, the rigid-flexible coupling firing dynamics model of a small-caliber gun was established, and the recoil displacement of the gun was tested by live firing test. Aiming at the error between the simulation curve and the test curve of the recoil displacement changing with time, taking the correlation coefficient of the two curves as the objective function, the dynamics model of the recoil mechanism was modified based on the time-domain response using the optimization algorithm. The modified results show that the difference of the maximum recoil displacement decreases from 9% to 0.1%, and the similarity between the simulation curve and the test curve reaches 0.99. The modified results based on the time-domain response effectively improve the accuracy of the recoil model, so that the established dynamics model can more truly reflect the dynamic characteristics of the recoil mechanisms, and provide the basic conditions for ensuring the simulation accuracy of the launch dynamics model.

A study of the ballistic protection mechanism of two kinds of structure against 7.62×54 mm ball ammunition

In this work, the protection mechanism of two kinds of structure was studied using 7.62×54 mm ball ammunition, which still played an important role in the threat spectrum of military vehicles. The tested one structure is consisted with silicon carbide (SiC) ceramic and Ultra-High Molecular Weight Polyethylene (UHMWPE), and the other is UHMWPE only. Silicon carbide ceramic was chose as strike face material for the reason of its widely using in Light Weight Vehicle Armor. And the UHMWPE was widely used for personnel body armor, because of its high protection ability and low density. These two kinds of structure were tested with 7.62×54 mm ball ammunition using a 7.62 mm powder gun launching system. After the ballistic experiment, the target plate was evaluated, and the residual steel core was recovered and measured. It was found that the main effect of ceramic strike face was eroding the steel core, rather than breaking it in the scene of defeating AP round ammunition. Otherwise, there is a critical thickness with the ceramic strike face to erode the steel core in the ceramic/UHMWPE combination, for the reason of the presence of two intermediate parts, the jacket and lead filler, between the core and ceramic target. Furthermore, compared to the ceramic/UHMWPE structure, single UHMWPE laminate is more effective, because that is strong enough to mushroom the core and absorb the energy.

Analysis of the vulnerability of MEMS tuning fork gyroscope during the gun launch

Micro-electromechanical systems (MEMS) gyroscope is fragile under mechanical impact. Especially, MEMS tuning fork gyroscope with movable structures, such as oscillating frames and folding beams, is susceptible to failure during the gun launch. However, the gyroscope usually presents better shock resistance in the shock test than in the ballistic environment. In this paper, the multiple high-frequency axial shocks and lateral shocks were studied to explain this phenomenon. A single-axis MEMS tuning fork gyroscope was used to analyze its behavior in response to the shock. First, theoretical analysis was performed regarding to the multiple high-frequency axial shocks and lateral shocks. Then the finite element analysis (FEA) was carried out to study the failure mode of the gyroscope under the typical shocks during the gun launch. The analysis results showed that the shocks with continuous oscillating acceleration had a significant amplification effect on the stress of the gyroscope structure. In addition, axial shocks can work with lateral shocks to cause severe stress on the weak positions of the gyroscope. Shock tests were carried out to simulate the in-bore ballistic environment, where the gyroscope experienced continuous oscillating acceleration. The experimental results showed that the critical acceleration of failure will be decreased when the gyroscope is in a state of continuous oscillations.

Influence of multiple structural parameters on interior ballistics based on orthogonal test methods

Abstract Influence of multiple structural parameters on the performance of a gun launch system driven by high-pressure reactive gases is important for structural design and performance adjustment. A coupled lumped parameter model was utilized to predict the propellant combustion, and a dynamic finite element method was applied to approximate the mechanical interactions between the projectile and the barrel. The combustion and the mechanical interactions were coupled through a user subroutine interface in ABAQUS. The correctness and the capability of the finite element approximations in capturing small structural changes were validated by comparing predicted resistance with experiments. Based on the coupled model, the influence of structural parameters of a medium-caliber gun on the system performance was investigated. In order to reduce the research costs, orthogonal tests were designed to investigate the comprehensive effects of the parameters. According to statistical analysis, the important order of the structural parameters on the launching process was obtained. The results indicate that the influence of the width of the rotating band stands out among the studied parameters in the gun. The work provides a method to investigate the influence of multiple parameters on system performance and gives guidance for controlling the system performance.

Dynamic simulation on vibration control of marching tank gun based on adaptive robust control

In order to better understand the dynamic behavior and decrease the muzzle vibration of marching tank, a mechanical–electrical–hydraulic integrated dynamic model of marching tank was established based on a novel dynamic co-simulation method. The hydraulic system model was modeled in Amesim and the dynamic model of marching tank was established in RecurDyn based on multi-body system theory, vehicle terramechanics, and gun launch dynamics. The control system model was modeled in MATLAB/Simulink. Therein, the adaptive robust control algorithm was introduced to design the vertical stabilizer controller and the simulation program of the designed controller was developed by C language. The simulation results show that the muzzle vibration of marching tank can be controlled effectively by the ARC method. Furthermore, the muzzle error compensation signal was added in the designed controller to weaken the detrimental effect of the barrel flexibility on muzzle vibration. This work provides an approach to investigate the dynamic behavior of marching tank considering effects among the mechanical, hydraulic, and control subsystems.

Laboratory Setback Actuators and Explosive Suitability for Gun Launch

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.

New Electronic Packaging Method for Potted Guidance Electronics to Sustain Temperature Cycling and Survive High-G Applications

Potted Guidance Electronics have been widely used in precision guided munitions. In the current generation of projectiles, soft potting materials have been sufficient to protect the electronics from the G-forces of gun launch at approximately 15 kG while sustaining uncontrolled extreme low temperature storage environments at different locations around the world. With on-going development of long-range precision guided munitions, stronger and hardened potting materials will be needed to survive gun-launch accelerations of 30 kG and higher. In the case of uncontrolled storage environments, the daily temperature fluctuations can act to dislodge/fail electronic components due to the coefficient of thermal expansion (CTE) mismatches between the potting materials and the electronic components. In this paper, a new protective layer method is presented, which consists of two tightly fitted preformed polymer layers, acting to mitigate the CTE mismatches, while only producing insignificant degradation of the supporting structure during extreme high-G projectile launch. The effectiveness of this new method is demonstrated by using finite element based modeling and simulation methods to examine a simplified potted electronics example. In the first step, the example was simulated with and without protective layers during an accelerated temperature cycling (−67 °F to 185 °F), and found that the protective layers were able to mitigate the CTE mismatch problem. During second step, the example compared dynamic responses between potted electronics with and without protective layers during a high-G, ∼15 kG, gun-launch simulations; results also showed that the degradation of the supporting structure introduced by protective layers during gun launch was insignificant.

A Riemann Problem Based Coupling Method for Predicting the Combustion of Propellant in a Gun Launching Process

AbstractMethods for improving the accuracy and guaranteeing the fidelity of numerical predictions are of great importance for physical problems accompanied by strong nonlinear multi‐physic interactions and extreme working conditions. The prediction of propellant combustion in a gun launching process is a typical example. A one‐dimensional two‐fluid model was utilized to govern the fluid field induced by the combustion. In order to guarantee the accuracy of the predictions, we utilized a Roe's scheme to solve the partial differential equations. To guarantee the accuracy of the moving boundaries in the expanding chamber, the coupling between the updating of the fluid field and the approximation of the mechanical interactions between the projectile and the barrel is realized based on the commercial software ABAQUS. The separate treatment of the advection and source terms in the split approach was verified through the agreement between the maximum value of the predicted average pressure in a closed bomb and the theoretical value. The coupled method dealing with the moving boundaries was validated by comparing the numerical results with the analytical results of a pressure‐driven piston case. Finally, the numerical method was applied to a large‐caliber gun. The predicted maximum pressure and the muzzle velocity agree well with experiments.

Dynamic simulation of tank stabilizer based on adaptive control

Tank stabilizer is a control system keeping the bore axis in the desired sighting angle. For the control problem of the stabilizer in the case of uncertain parameters, the adaptive control method is introduced to design the vertical tank stabilizer with the nonlinear dynamic model of vertical stabilizer given in the paper. In the design, the multiple parameter uncertainties of the hydraulic servo system are fully considered and the linear feedback control is used to improve the asymptotic stability of the system. The vertical stabilizer of tank is simulated in MATLAB/Simulink environment. In addition, a dynamic model of tank on the move is established based on multi-body system theory, vehicle terramechanics and gun launch dynamics. Then the established dynamic model is combined with the designed controller based on the RecurDyn/Control module. The numerical calculation results show that the adaptive control method can effectively control the muzzle vibration of tank on the move and it can satisfy the requirement of actual vertical stabilization accuracy. But some nonlinear factors of the gun such as the flexibility of the barrel will seriously influence the desired stabilization accuracy of the vertical tank stabilizer. A comparison experiment between adaptive control and proportional–integral–derivative control is also presented to show the effectiveness of the adaptive control method. The research provides a feasible way to improve the firing accuracy of tank firing on the move.

Investigation of the Driving Ability on Concave Armature

Driving ability of the armature is one of the important launching characteristics on rail gun. To push heavier load effectively with less mass is an important goal to pursue for the armature design. The armature used to be launched or push load is mainly designed in C shape. Whether the C-shaped armature is the best choice for the electromagnetic rail gun launching or not? Based on the above question, this paper proposes a novel concave armature. Similar to the principle of arch bridge, the concave shape is used to design the armature arm in order to withstand the electromagnetic force. The concave arm structure can transfer the electromagnetic force to the force that pushes the load and the pressure that the armature applies to rails, so that the concave arm avoids fracture due to the large electromagnetic force, and the driving ability for the armature is improved. This paper focuses on the comparison of driving ability between the concave armature and C-shaped armature. The C-shaped armature and concave armature, with the same mass and similar structure, also with the same load mass, are designed. Electromagnetic and mechanical coupled calculation under the same condition is conducted. Through analyzing the stress and deformation, a primary conclusion is drawn that the concave armature can push a heavy load and has small deformation. An experimental research is carried out to verify the driving ability of pushing heavy load for two armatures. It provides valuable reference for engineering design.