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Interior ballistics experiment is an indispensable link in the experimental teaching of weaponry in colleges and universities.Because of the risk of experimentation, the rapidity of the process, and the high cost of equipment, it is difficult to develop the interior ballistics in the actual teaching process. Taking the two typical experiments of projectile muzzle velocity test and rolling test as examples, the virtual reality technology was introduced into the traditional interior ballistics experiment, and an image and intuitive real-time virtual experiment scenario was established. The actual physical process was simulated through the calculation of interior ballistic simulation. Using the Unity3 D engine, an interior ballistic virtual experiment system with good visual immersion and interactivity has been developed. The teaching practice of the Weapons Virtual Simulation Experimental Teaching Center of North University of China shows that the internal ballistic virtual experiment system saves experimental expenses, improves the flexibility of time and space, and has good practical and promotional value. [ABSTRACT FROM AUTHOR]

In order to provide an accurate mechanical environment of exterior ballistics for fuze safety design, a mathematical model of the motion of unrotating projectile around the center of mess in exterior ballistics is established based on the rigid body dynamics. The formulas of the radial and axial components of the inertial force acting on fuze parts, which is caused by the motion of non-rotating projectile around the center of mess, are derived. The results show that the ratio of the maximum radial component of the inertial force to its maximum axial one is the largest nutation angle. And the radial component closes to zero when the axial component reaches to the maximum, and vice versa. So the frictional force caused by this inertial force can be ignored during the analysis for motion of fuze parts caused by the same inertial force. [ABSTRACT FROM AUTHOR]

For the networking measurement mode of exterior ballistic in weapon test, the optimal disposition of test equipment is studied to ensure the optimal ballistic measuring precision. Based on the pointby-point least squares solution model, the root-mean-square of total cumulative error of ballistic parameters is designed as precision evaluation criterion. Considering the nonlinear constraints of solution space in actual situation and focusing on the probability characteristics of genetic algorithm, a complete multisample genetic algorithm based on Monte Carlo test and population penalty function check is designed to reliably solve the problem of optimal disposition. The proposed genetic algorithm is used to simulate and evaluate an optimal disposition of test equipment. Monte Carlo experiments were made for 500 times, a globally optimal solution was obtained by statistically analyzing the experimental results, and the proposed algorithm was compared with the traditional method. The simulated results show that the proposed algorithm can be used to reduce the influence of probability characteristic of genetic algorithm, lock the global optimal solution with large probability events, and ensure the validity and reliability of the optimal solution. [ABSTRACT FROM AUTHOR]

Series chamber is a new technology on the basis of the mature technology of solid propellant. It can improve the propeller' s kinetic energy through rebuilding the existed guns. It is important to the weapons' performance improvement. The two phase flow model of the interior ballistics process of 140 mm series chamber gun is established and simulated by MacCormack scheme. In addition, the completed programming has been used to analyze the influence of main-secondary powder proportion, ignition delay of secondary power and piston mass on interior ballistics performance. The result shows that the new technology can improve propeller's velocity while not adding chamber's pressure. [ABSTRACT FROM AUTHOR]

In order to improve the simulation precision of artillery interior ballistics, on the base of the artillery erosion interior ballistics theory in Ref.\[1\], the kinetic equation of projectile and the basic equation of interior ballistics are set up by keeping the equations of the variable projectile starting pressure, and the geometric combustion law and burning rate law of gunpowder unchanged, and analyzing the full-bore erosion wear characteristics of artillery, such as variable bore sectional area, variable chamber volume and volume increment after body, and then an interior ballistics model based on the whole-bore erosion wear is established. The resolving method of interior ballistics is derived. The certain artillery test data are computed through simulation. The simulated results demonstrate that the error simulated and test velocities are less than 0.9%, which satisfies the requirement of 3% simulation error of artillery engineering practice. The proposed method is better than the artillery erosion interior ballistics theory in Ref.\[1\]. The result proves that the proposed interior ballistics model and resolving method have higher simulation precision, and could be used for the prodiction of artillery barrel life. [ABSTRACT FROM AUTHOR]

Considering that the length of the tubular charge for the large caliber high speed Davis gun is long, the traditional pseudo-fluid hypothesis in two-phase flow model may cause errors. In order to solve this problem, Eulerian coordinate system is used to settle the gas field, and the Lagrangian coordinate system is used to settle the solid field. It is assumed that the tubular charge clusters are linearly configured along radial direction, these clusters move along axial direction，and gas moves along radial and axial directions. Based on this assumption, a two-dimensional interior ballistics model is established for a 480 mm Davis gun with tubular modular charge. Then through the comparison of the simulated and experimental results, the proposed model is verified to be effective. The distribution of gas pressure along two directions and the movement rules of tubular charge clusters along axial direction were obtained by further analysis of the simulated results. [ABSTRACT FROM AUTHOR]

An interior ballistic model is established on the basis of modified corresponding virial equation for the high-pressure air ejection device under the wide variation conditions of pressure and temperature. The second and third virial coefficients of modified corresponding state equation are calculated. Based on the virial equation of volume series form which is truncated to the third virial coefficient, the analytical expressions of specific thermodynamic energy and specific enthalpy are presented, and the dynamic thermodynamic parameters are obtained. The numerical experiments are performed. The changing rules of thermodynamic properties and missile acceleration and velocity are obtained. The results show that the compression factor reaches 1. 107, and both the actual decreased values of temperature and pressure are higher than the ideal decreased values in the hyperbaric chamber, and the work capability of hyperbaric air deviates from the ideal gas, and it is necessary to study real gas effects. [ABSTRACT FROM AUTHOR]

In order to provide an accurate mechanical environment of exterior ballistics for the safety and reliability design of fuze, a mathematical model of the motion of rotating projectile, which has dynamic unbalance angle and the axis of rotation of fuze being umparallel to the axis of projectile, around the center of mess in exterior ballistics is established based on the rigid body dynamics. The formulas of the axial, radial and tangential components of inertial force acting on fuze parts, which is caused by the motion of rotating projectile around the center of mess, are derived. The credibility of the theoretical analysis is verified by the simulation of ADAMS software. It can be known from force analysis that, when the center of axial moving parts of fuze and the centroid of bullet and axis are on the same plane, and the distance between the centroid of axial moving parts of fuze and the inertia principal axis of projectile is maximum, the axial force and radial inertia force of fuze are greatly increased compared with the traditional calculation results (the inertia force of 155 mm caliber projectile achieves several times). The fuze axial moving parts can not be prevented from moving forward under the action of axial force even if the radial and tangential forces are far greater than axial force in the condition of periodic fluctuation and large fluctuation amplitude. [ABSTRACT FROM AUTHOR]

In order to achieve the launch of individual rocket in limited space, a individual rocket launching system of which the liquid column is placed in the tail tube as a balance body is proposed. The system is tested, and the interior ballistics process is analyzed over time intervals. Based on the theory of the classical inrerior ballistics theory, a mathematical model of the launching system is established by assumoffing that the irregular mixing of gas and liquid is regarded as mixing of perforation. Runge Kutta method is used for numerical calculation, and the complete curves of interior ballistics process are given. The analysis result shows that the theoretical results are in good agreement with the experimental results. The relative error of the maximum pressure in combustion chamber is 1.6%, and the relative error of projectile velocity is 0.9%. The calculated results shows that the liquid column can be used to reduce the launching characteristics of rocket, improve the velocity of projectile, and enhance the power of individual rocket for the individual rocket launching systems with and without liquid column under the same launching conditions. [ABSTRACT FROM AUTHOR]

Gun water-projectile test is widely used to determine its technology state and inspect its repair quality after repairing. It is difficult to determine the key internal ballistic parameters in the mass of water-projectile because an internal ballistics design method on water-projectile test lacks for the new guns, which is restricted to carry out water-projectile test. An internal ballistics model of water-projectile test is established based on the principle of water-projectile test and its engineering practice. The internal ballistics design method based on the impulse equal principle of gun bore resultant forces in water-projectile test and live firing is introduced. The research result can preovid theoretical guidance for water-projectile test after new gun repair, and provide the reference for the water-projectile test of the other assessment purposes. [ABSTRACT FROM AUTHOR]

High pressure accumulated by propellant burning in high pressure ejecting apparatus makes the chamber open instantly and eject a projectile to a target. In order to grasp the complex change of gas flow in the launching chamber, a two-dimensional interior ballistics model is established and simulated by Runger-Kutta and MacCormark schemes. The calculated pressure results are reliable by comparison with the experimental ones. The flow field characteristics are got through the analysis of the calculated results, such as gas pressure, velocity, etc. The results show that the size and distribution of high pressure gas accumulated at the bottom of the projectile have the direct effects on the ejection performance. [ABSTRACT FROM AUTHOR]

Based on the principle of two-stage light gas gun, an interior ballistics numerical analysis program was developed to analyze the performance and operation of two-stage light gas gun. The included numerical models were: a quasi-one-dimensional, two-phase hydrodynamics model to simulate the combustion of solid propellant in the gunpowder chamber and pump tube, an unsteady, quasi-one-dimensional, compressible flow model to analyze the flow of hydrogen gas between the piston and projectile, a one-dimensional, ideal-viscoplastic, extrusion model to simulate the motion of piston in high pressure section, and a friction model combined the classical law of frication to describe the motions of piston and sabot in the pump and launch tubes. The friction and heat transfer to the tube wall for gases and solid media are also modeled. The governing equations of gas flow were solved by CFD methods, which have second-order accurate in space and time. The interior ballistics characteristics of two-stage light gas guns of CARDC were analyzed under the typical test operating conditions, and the numerical projectile velocities were agreed well with that of test results. With the help of this program, the motion process of piston and the history of projectile acceleration loads could be obtained. The proposed method provides a way to optimize the operating conditions and improve the performance of two-stage light gas gun. [ABSTRACT FROM AUTHOR]

A kind of one-side ejection device with two-step cylinder is proposed to increase the effective thrust travel of missile pneumatic launching system. The real gas state equation, Peng-Robinson equation, is used as theoretical basis. The mathematical expressions of pneumatic interior ballistics model are deduced on the basis of 'P-R' state equation for the two-step cylinder. The interior ballistics equation is solved by using Simulink software, and the one-side launching ejection is built by means of ADAMS. The co-simulation model of device is achieved. The results show that the pressure of first-order lower-chamber rises first and then falls. It can be seen from the calculated result that both the thermodynamic parameters and the missile acceleration obviously fluctuate in the process of cylinder changing, but their influences on missile speed and displacement are very small. To reduce the equipment volume, the air source volume is selected as the objective function. The air source volume optimized by genetic algorithm is decreased by 64.5%, thus improving greatly the mobility of launcher. [ABSTRACT FROM AUTHOR]

An improved two-phase flow model is established to simulate the interior ballistic characteristics of modular propellant charge. In this model, the constraint of the walls of modules on gas flow is taken into account. The rupture rule of combustible case and the flame spreading between different modules are also considered in the improved model. This model turned out to be reliable by comparing the numerical results with the experimental data. It can be used to predict the development of pressure waves and to diagnose the interior ballistic performance of modular propellant charge systems. The simulation results show that the flame spreads slower because the gas is constrained by the bottom walls of the center-tube. The combustible cases are ruptured in sequence, the time when the combustible cases begin to rupture until all the cases rupture is affected by the strength of the modular case and the ignition core. [ABSTRACT FROM AUTHOR]

In order to ensure high dispersing velocity of the submunitions in the low overload dispersing environment, a new piston central dispersing mechanism was devised and working process of the dispersing mechanism was researched. The characters of this kind of mechanism were as follows : the trust force from the piston to the submunition was transmitted by the beveled sabot; the powder burned in the high-pressure chamber and the generated powder gas did work in the low-pressure chamber; the initial trust peak was reduced, and so on. According to the working principle of the piston central dispersing mechanism, the force analysis of piston, sabot and submunitions were carried out, and the interior ballistics model of the new mechanism was established. It is proved by the simulation calculation that, this new piston central dispersing mechanism not only can supply a dispersing velocity more than 50 m/s, but also can control the overload of submunitions under 1 000g. The interior ballistics model can be used to guide the design of the new piston central dispersing mechanism. [ABSTRACT FROM AUTHOR]

For the location problem of unexploded ordnance (UXO) in the processes of conventional weapon test, military training and exercises, a low cost UXO detection method of the terminal ballistics is presented. According to the size of the impact area , many low cost acoustic sensors are installed in shooting range. The measuring range of these sensors covers the whole impact area. As for the signals of aerodynamic noise and the landing sound, which are captured by each acoustic sensor, the computation is implemented to used FFT and Laplace wavelet to denoise and enhance the original acoustic signal; use the short time energy, short time amplitude, and short time zero-crossing rate to detect the endpoint of these signals above; use the wavelet packet to collect the features of the enhanced signal; and use the minimized distance-based threshold criterion to identify the aerodynamic noise and the landing sound. The test results of UXO location in the shooting range show that the proposed technique can be used for UXO location and the location accuracy can reach 10 m. [ABSTRACT FROM AUTHOR]

The hydro-ballistic trajectory and cavity of the half sphere bullet and general pistol bullet are experimentally researched by a high speed digital video recorder when they entrain water at six speeds and at two depths of water. The experimental results show that the shape of a bullet has important influence upon the hydro-ballistics stability of the bullet motion. The hydro-ballistics of the half sphere bullet is stability, but the stability is not well for pistol bullet. The shape of pistol bullet cavity is "lotus root". The velocity attenuation law of the bullet have similarity at a range of bullet entraining water speeds. The velocity attenuation law in water has similarity for both of the half sphere and pistol bullet. The speed of bullet in water decreases very quickly. A calculation model is established to predict the velocity attenuation law of the bullet. The calculation results are compared with the experimental results, they agree well with each other. [ABSTRACT FROM AUTHOR]

The working condition of barrel forcing cone is worse during the firing process of small arms. To study the influence of the forcing cone angles on the stress of barrel forcing cone, the three-dimensional finite element models of barrel and projectile at different forcing cone angles are established, in which the structures of barrel and projectile, and nonlinear constitutive relations are considered. The effects of different forcing cone angles on the projectile engraving process are analyzed. The data of engraving resistance is obtained under the condition of different forcing cone angles. A response surface model of engraving resistance is established. The formula and the variation rules of projectile engraving resistance along with the forcing cone angle and engraving displacement are calculated based on the above data by using Hermite polynomial. A dynamic model of projectile engraving process is established in consideration of the engraving resistance. The engraving pressure during the projectile engraving process is solved by programming. The forcing cone angles among 0.11° and 1.13°, which satisfy the requirement of muzzle velocity of the projectile, are obtained, and then the best forcing cone angle of 0.56°, which could reduce the barrel stress to ensure the highest velocity and meet the design range of forcing cone angles in case of satisfying the interior ballistic behaviors, is got. [ABSTRACT FROM AUTHOR]

The decay function for the free-surface effect is constructed by treating a target as an incompressible Mohr-Coulomb material and assuming that the cavity expansion produces a plastic-crack-elastic response region. The semi-empirical forcing function of brittle targets for oblique penetration is obtained by multiplying the semi-empirical forcing function of brittle targets with the decay function. Then the projectile is modeled with an explicit transient dynamic finite element code and the target is represented by the forcing function as the pressure boundary condition. This methodology eliminates the need for discretizing the target as well as the need for the contact and erosion algorithms, which reduces the computer time and memory requirements. The oblique penetration of 4340 (RC44.5) steel into limestone target is simulated. The comparisons of the final forms of projectile and the final positions of tip in simulation and experiment demonstrate the effectiveness and advantage of the proposed method. [ABSTRACT FROM AUTHOR]

In order to distinguish 1 cm² copper crusher gauge, a special experimental device which can supply required pressure source by volume expansion is proposed and designed. An interior ballistic model of the device is set up and simulated based on the interior ballistic analysis and the flow equation of the working chambers. The pressure and flow characteristics of propellant gas between bore and chamber are obtained. And the influences of initial volume and position of the high pressure chamber on its maximum pressure are studied. The maximum pressure of the high pressure chamber can be adjusted to about 39.0 MPa under the condition of the known parameters. Compared with the experimental results, the maximum deviation is 4.9%. The device can meet the requirement of identifying copper crusher gauge. [ABSTRACT FROM AUTHOR]

In order to evaluate ballistic consistency under small sample circumstance, an evaluation method of ballistic consistency is proposed based on the normal distribution small sample compatibility theory. This method is to compare the calculated order statistics and the simulated critical value to determine the ballistic consistency. The main advantage is not necessary to calculate the position- scale estimate value, so it could decrease the calculation error due to small sample size. The calculation shows that this method is better than matched pair t test and probability circle sequential test under small sample circumstance (n≤5 ). [ABSTRACT FROM AUTHOR]

Considered the coupling effects of classical interior ballistic equations and band's engraving process, the solution of interior ballistic equations was taken as the boundary condition of the simulation for engraving process, and the results of the simulation were taken as the initial conditions for the interior ballistic equations in the next step iteratively. A coupled constitutive model considered visco-plasticity and ductile damage and based on continuum damage mechanics was introduced to simulate the band's damage process. The Von Mises yield criterion, Johnson-Cook hardening model and Johnson-Cook fracture strain model were adopted, and the model considered large strain, high strain-rate, thermal softening and damage evolution. The model was implemented in the explicit finite element code by using VUMAT subroutine of Abaqus\Explicit module. The band's engraving processes of two different bore structures were simulated, and the influences of different engraving conditions on the stress state of the band were analyzed. The effects of band's stress state and bore structure on the interior ballistic performances were pointed out. It is very useful for the design of bore structure. [ABSTRACT FROM AUTHOR]

Ballistic gelatin is used as a stimulant for human tissue in the experimental study of temporary cavity which is an important factor of ballistic injury. To study the motion of temporary cavities, the steel spheres with diameters of 3 mm, 4 mm and 4. 8 mm are fired into the gelatin blocks at 650 ~ 1 000 m/s in the experiments. The movement of temporary cavity is recorded by a high speed camera. The sine motion of the cavity wall is deducted based on the displacement field assumption and the elastic deformation assumption of gelatin. The empirical relations between amplitude and energy, and frequency and energy are established using the experimental data while a penetration model of spherical fragments in gelatin is built. The model is used to predict the temporary cavity for a 5. 2 mm tungsten sphere penetrating into gelatin at 800 m/s. The predicted results are in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

The two-phase flow mathematic models are developed for gas generator with central igniter tube. The one-dimensional two-phase model is used for the ignition of central igniter tube, and the two-dimensional two-phase model is used for the energy release of tubular gas generator. The coupling function of two tubes is established through exchange between gas and solid. The interior ballistic simulation software is programmed by Mac Cormack two-step scheme and is used to calculate the gas generator. The calculated results well accord with the test results, which proves that the model is right and provides important theory foundation to structure design and optimization on gas generator with central igniter tube. Meanwhile, the energy releasing course is analyzed based on the simulation results. The result shows that the uniform ignition condition is the precondition of gas generator releasing energy steadily. The ignition energy released uniformly could ensure the reliable burning of powders in gas generator and the release of controlled energy. [ABSTRACT FROM AUTHOR]

To get the surface temperature characteristics of projectile flying at high rotational speed, based on the six degree of freedom (6-DOF) rigid body trajectory model, the heat balance equations were established by using node thermal network method. With the heat exchange theory of flow around a cylinder, the influence of rotation was considered for the calculation of aerodynamic heating. The temperature field distribution under the control of trajectory data and airflow properties was obtained by solving the trajectory equations and the heat balance equations simultaneously. Finally, the factors which have impact on the surface average temperature field, including launching velocity, initial rotational speed, launching angle and airflow temperature, were also studied. The results show that the surface temperature increases with launching velocity non-linearly. The temperature gradient is inversely proportional to the distance from the warhead. The bigger the initial rotational speed is, the higher the peak temperature and the rate of temperature change are. The higher the airflow temperature is, and the smaller the launching angle is, the higher the average temperature is. [ABSTRACT FROM AUTHOR]

The warship continues to move after the trajectory correction projectile is fired from shipborne gun, and the shipborne radar for trajectory measurement also continue to move and sway, and so the relative trajectory measured by radar need to be transformed into the ballistic reference frame which takes the gun muzzle as an origin during firing. The precision of transformed ballistic coordinates is influenced by the warship fluctuation and the errors of radar measuring, warship sway angles, velocity and course bearing. In order to quantify the influence of every error on the precision of ballistic coordinates, a model of precision of ballistic coordinates was set up and simulated, and some data about the influence of warship fluctuation and the errors of radar measuring, warship sway angles, velocity and course bearing on the precision of ballistic coordinates were got. [ABSTRACT FROM AUTHOR]

A novel 2-DOF ammunition coordinator structure scheme is proposed, and the controlled dynamics behavior of the coordinator is studied by considering the influence of the random vibration of its installation base. The random vibration of base is treated as one kind of external disturbance forces acting on the coordinator, and the action of the coordinator on the base is negligible. On the assumption that the external disturbance force and the control force are bounded, a nonlinear control algorithm and the structure-control coupling dynamics equations of the coordinator are established based on the second kind La-grange equations and a special implicitly given Lyapunov function. The dynamics equations are solved by a numerical algorithm based on Newton's method and the Runge-Kutta method. The simulation result shows that the proposed 2-DOF ammunition coordinator can be used to realize the accurate coordination and positioning control of the ammunitions. [ABSTRACT FROM AUTHOR]

In order to explore the bullet proof mechanism of ceramic/steel composite armor, the ballistic impact experiment was carried out to study the dynamic response of ceramic/steel composite armor subjected to the impact of high speed fragments. The damages of projectile, ceramic and steel back plate were described physically and analyzed phenomenologically. The damage modes of ceramic and steel back plate were determined. The energy transformation during the ballistic penetration and the bullet proof performance of the ceramic/ship steel composite armor were analyzed. The results show that the conical crash is a main damage mode of ceramic under the impact of high speed fragments. And the main macro cracks are radial, ring and conical cracks which extend outward at about 65° angle included between the conical crack and the initial surface normal. Besides there are the inverse conical cracks extended outward at angle of 65° to the back surface normal. The deformation range, destructiveness and damage mode of the back plate have great different from those of ship steel target. The deformation mode of the backing plate is bulging-dishing when the impact velocity is below the ballistic limit. When the impact velocity exceeds the ballistic limit, the back plate has 3 damage modes, i. e. shearing damage, dishing-shearing-petaloid damage and dishing-petaloid damage, as the relative thickness of ceramic increases. In the penetration process of light ceramic/metal composite armor, the kinetic energy of projectile is mainly dissipated in the deformation and damage of projectile and back plate. When the velocity of the penetrator is about ballistic limit, the energy dissipated in projectile and back plate damages varies with the relative thickness of ceramic. But the total energy dissipated in these facets occupies more than 90% of initial kinetic energy of the projectile, and the energy dissipated in the fragmentation of ceramic and the ejecting kinetic energy of ceramic fragments occupies less than 10% of its initial kinetic energy. [ABSTRACT FROM AUTHOR]

Probability of perforation ( POP) curve is a constructive method to estimate the ballistic performance. It can be used to estimate the low velocity at smaller penetration probability. POP curves have potential and promising application in body armor design. For this purpose, the performance of UH- MWPE unidirectional layers (PE armor) against 7.62 mm type 51 pistol bullet was investigated. POP curves was established by logistic function and binary logistic regression. v50 (velocity with 50% penetration probability) and v05 (velocity with 5% penetration probability) of PE armor were derived from POP curves. v50 was 592 m/s determined by both methods, while v05 was 538 m/s and 514 m/s, respectively. The results indicate that the regression method is more suitable for the estimation of velocity at low penetration probability. The difference between the two POP curves was discussed. [ABSTRACT FROM AUTHOR]

Low-velocity ballistic experiments were carried out to study the perforation-resistant mechanisms of warship topside composite armor system, which was simulated by composite laminates at the front and homogeneous steel plates at the back. Failure modes and energy absorbing mechanisms were investigated and the influence of the area density of front composite armors on total perforation resistance of combined targets was analyzed. Based on the experiments, an equation was obtained to predict the residual velocities in the case of low-velocity perforation of combined targets by hemispherical-nosed projectiles according to the failure modes of the targets. The results show that under low velocity perforation, combined targets mainly exhibit local damage. A few amounts of fiber at the impact side of front composite armor are sheared by the projectile. Failure modes of front composite armors are mainly fiber tensile rupture while for steel backing plates, failure modes are primarily petaloid damage. The whole energy-absorbing capability of combined targets increases with increasing the area density of front composite armors. It is shown that theoretical predictions coincide with the experimental results in terms of residual velocities. [ABSTRACT FROM AUTHOR]

A contamination prevention method using jet flow was proposed to protect the optical window in laser ignition system from attachment of combustion remains of propellants and decrease of transparence. The pressure in chamber and gas flow between the chamber and the cavity were analyzed by using interior ballistics calculation. The mathematical model of the particle movement in the chamber was established and calculated. The calculation and simulation results indicate that the new proposed method is effective to protect the optical window, the jet flow interference can reduce the particles reaching to the optical window area effectively. The structural parameters are optimized for guns with different calibers based on the simulations. A screen tube is proved to be useful to enhance the protection effect. The increases of the length of cavity or the angle of diverting orifice can lead to a better protection. [ABSTRACT FROM AUTHOR]

To simplify the complexity of moving boundary treatment in the two-phase flow numerical simulation and improve the computational accuracy of moving boundary treatment, a two-dimensional twophase flow model based on ALE method is established. The governing equations are discretized with the TVD-type MUSCL scheme to obtain a second order accuracy in finite volume form. A two-step and fourthorder Runge-Kutta method is used to solve the source terms. The dynamic mesh update method and numerical method are verified by a standard test with the exact solution. The numerical application on a large caliber guided projectile shows the complete development and the two-phase flow characteristics of the interior ballistic process. The calculated results are in good agreement with the experimental results. The effects of different ignition conditions on interior ballistic performance are investigated. The study lays a theoretical foundation for deep optimization of the interior ballistic performance and firing safety. [ABSTRACT FROM AUTHOR]

The numerical simulation accuracy of interior ballistics of ultrahigh firing rate guns depends on the accuracy of calculating the drag force acting on projectile nose. In order to improve the numerical simulation accuracy of interior ballistics of ultrahigh firing rate gun, the secondary development tool UDF is used to couple FLUENT and the classic interior ballistic (CIB) model for the calculation of flow field in front of projectile. The nose drag force of the second launched projectile is obtained, and the variation law of nose drag force at different firing rates is analyzed. The simulated results show that the propellant gas flow field distribution can be obtained by the two-way coupling of FLUENT and CIB model, and the accuracy of calculating the nose drag force is improved. The nose drag force increases quickly after launching, and then decreases after it reaches a maximum value until the projectile leaves the muzzle. This variation law is common at different firing rates. When the firing rate reduces, the increased amplitude of nose drag force decreases at the earlier stage of projectile movement, and its decreased amplitude also decreases at the later stage of projectile movement. [ABSTRACT FROM AUTHOR]

A new prediction method based on radial basis function (RBF) neural network and an unscented Kalman filter technology is proposed for the precise and quick prediction of impact-point without exact flight data. Firstly, RBF neural network approximated external ballistics equation is used to predict the projectile impact-point, and the improved quantum-behaved particle swarm optimization algorithm is used to optimize the training method. On this basis, the tentative prediction data is processed with unscented Kalman filter. At last, the prediction simulation is carried out. The results show that a high prediction precision can be reached under the condition of input data with noise. The method proposed in this paper is efficient and available for impact-point prediction. [ABSTRACT FROM AUTHOR]

For the technical scheme of the two-dimensional trajectory correction projectiles (TDTCPs) with drag brake and despining blade, the mathematical model of two dimensional trajectory corrections is discussed based on the theory of exterior ballistics. An approximate formula for predicting the ballistic drift and trajectory correction quantity is deduced with respect to the process of lateral trajectory correction. The capability of lateral trajectory correction and the flight stability of TDTCP are also analyzed. By comparing with the results of flight test, the accuracy and effectiveness of this approximate calculation method are verified. The result of the approximate method is in accordance with those of 6DOF trajectory model and firing test, and the maximum error is no more than 40 m. All the work is valuable for further research. [ABSTRACT FROM AUTHOR]

A three-dimensional two-phase flow model based on arbitrary Lagrange-Euler method is established to improve the computational accuracy and cost of three-dimensional simulation for interior ballistic in guns. The three-dimensional governing equations are discretized with the MUSCL scheme. The fourth-order Runge-Kutta method is used to solve the time orientation. The numerical method is coded and compiled in the MPI parallel environment. The numerical simulation shows the detailed three-dimensional development of the two-phase flow behavior. The calculated results are in good agreement with the results in Ref.［20］. The effects of different igniter lengths and diameters on interior ballistic performance are analyzed. Parallel numerical studies show that the parallel efficiency can be reduced by about 50% using interior ballistic three-dimensional calculation of 24 processes. [ABSTRACT FROM AUTHOR]

In order to study the two-dimensional rheological behavior of a long-rod projectile penetrating into steel target, a two-dimensional elbow-streamline penetration model was developed based on long-rod projectile hydrodynamic penetration model, mass conservation during penetration and elbow model. The impact velocity, reference point angle and reference point radius are considered in the proposed model. The material flow around the nose of tungsten long-rod projectile penetrating into a steel target was analyzed based on the proposed model and compared with the test results. The results show that the material flow around the tungsten long-rod projectile nose is non-uniformly distributed, and the flow velocity on the outer side is less than that on the inner side. The pressure on the long-rod projectile nose material is distributed gradiently. The proposed model is used to describe the material flow of long-rod projectile nose during penetration, and explain the process of transition from fluid to solid in the projectile nose at the final stage of penetration. It reveals the relation between the change of ballistics channel and the penetration state transition of projectile. [ABSTRACT FROM AUTHOR]

The concept of dual-spinning becomes a new approach to upgrade a conventional spin-stabilized projectile, wherein an actuator is used to control the phase of forward canards. To design and analyze the inner control channel efficiently, a dual-spin ordinary differential equation, including a quasi-steady aerodynamic model and an optimized LuGre friction model, is established. All aerodynamic and kinematic data in time-domain, as input in least square estimation, is obtained in transient numerical model and dynamic wind tunnel test. The results indicate that the side force and roll moment supplied by canards are affected by phase angle and roll rate, and the estimated accuracy of quasi-steady aerodynamics is lower than 4×10-3. The friction between forward and aft parts is a function of axial pressure and relative roll rate, which can be estimated by the optimized LuGre model. The feasibility of using the dual-spin model to predict the canard movement is validated by measurement in a flight test. The proposed approach promotes the pace of engineering application of dual-spin projectiles. [ABSTRACT FROM AUTHOR]

The influence of bore damage on interior ballistic performance and muzzle-leaving state of bullet is studied, and the mechanism of how bore damage leads to the end of barrel's life is explored. The accurate thermo-mechanical coupling finite element analysis (FEA) models of barrels with bore damage at different life periods are established based on the distribution and evolution rule of bore damage obtained through systematic life tests. The changing rules of interior ballistics performances and muzzle-leaving states of 12.7 mm bullet with the evelopment in bore damage are obtained through numerical simulation which combines the interior ballistics process and the explicit finite element method through Fortran subroutines. The coupling model of bullet and gun barrel is proved to be effective by comparing the calculated results of interior ballistic parameters with experimental results. The simulated results show that the initial disturbances of bullet at muzzle, the reduction in rotational velocity and the variation in bullet's surface topography increase as the firing cycle increases, especially in barrel's later lifetime. Variation in muzzle-leaving state of bullet is the key factor for barrel's life end. Research results have important significance on further studying how bore damage degrades bullet's exterior ballistics performance and the end-of-life mechanism of barrel. [ABSTRACT FROM AUTHOR]

Reverse ballistic impact test has been widely used to research the materials and structural dynamic response, in which the measuring devices can be installed on the free-free beam to obtain the more accurate measured results. The 20° reverse ballistic oblique impact tests of free-free beam are carried out, and the digital image correlation (DIC) technique is used to measure the real-time dynamic response. The failure criterion is introduced and the simulated results are considered to solve the dynamic responses of free-free beam under axial and transverse impact loading. The results show that the calculated bending shape agrees well with the experimental result, and is better than that in Ref［4］. The reverse ballistics is equivalent to the forward ballistics for the reverse ballistic mass ratio mγ⩾10. The proposed method can also be used for solving the dynamic response of projectile during penetration. [ABSTRACT FROM AUTHOR]

The ideal animal model of abdominal firearm injury is essential for conducting research on the war injury rescue techniques, the training in injury control surgery, and the trauma ballistics research. But so far, there is no standardized animal model that can realistically simulate abdominal firearm injuries in domestic and foreign research. This article reviews the common animal models of abdominal firearm injury from the aspects of injury weapons, experimental animals and modeling purposes, and expounds the advantages and disadvantages of each model, in order to provide reference for the research on abdominal firearm injury. [ABSTRACT FROM AUTHOR]

The canard and bearing are dynamically modeled to improve the dual-spin trajectory model based on Euler approach. The working condition of electromagnetic actuator of trajectory correction projectile with decoupled canards (TCPDC) is investigated. The designed working condition is validated by the parameters derived from the dual-spin trajectory. The spin-rate and electromagnetic torque of actuator are extracted based on the rolling states of projectile and canards. The calculated results indicate that the canards spin in relative to the opposite direction of projectile body rapidly after launch, and then spin down at a relatively low and stable rate, which is hardly affected by the launching conditions. The spin rate of projectile is the main factor, which leads to a large range of actuator' s working speed. After the projectile flies through an apogee, the spin rate of actuator could be stably maintained between 130 and 230 r/s, and the essential torque is less than 0. 5 N·m. In terms of the working range of actuator, the optimal starting control point should be in the segment behind the apogee. [ABSTRACT FROM AUTHOR]

The output performance of Al/KClO4 igniter is a key parameter for the overall design of pyrotechnically actuated separation device. In order to describe the output performance of Al/KClO4 igniter more accurately, an improved interior ballistics analysis model of Al/KClO4 is established by modifying the hypotheses of classical interior ballistics equations and introducing the correction coefficient of powder force. The Matlab numerical algorithm is written to calculate the pressure peak, pressure rise time and impulse per unit area of Al/KClO4 igniter in closed bomb. The changes of these parameters with charge mass and cavity volume are analyzed. And the calculated results are in good agreement with the experimental results. The results show that the pressure peak of Al/KClO4 igniter increases with the increase in charge mass, and decreases with the increase in cavity volume. In a small volume (<5 mL), the cavity volume is increased by two times, and the peak pressure is decreased by about 40%. [ABSTRACT FROM AUTHOR]

To study the influence of annular cavity of gas-ejection launcher on secondary combustion, RNG k-ε turbulence model, finite-rate/dissipation model and dynamic mesh update method are adopted to establish a secondary combustion model of initial cavity, in which the movement of rear cover is considered. Compared with experimental result of ejection launcher without annular cavity, the variation in fluid structure, ejection interior ballistics and variation in load are studied for the initial cavity with/without annular cavity and the initial cavity with different opening directions. The mechanism of that annular cavity reduces the secondary combustion impact is analyzed. Results show that, from the point view of fluid structure, an annular cavity can is added to change the direction of gas diffusion and decrease the area between gas and air. The backflow region with annular cavity can decrease the pressure peak caused by secondary combustion. From the point view of interior ballistics, the acceleration of missile in which the annular cavity opening is formed upwardly changes gently, the velocity out of tube is reduced by 5.9%, and the time out of tube is delayed by 4.5% [ABSTRACT FROM AUTHOR]

The effects of the state parameters of projectiles at muzzle on the dispersion of projectiles are analyzed. Based on the six-degree-of-freedom ballistic equations, the sparse grid numerical integration (SGNI) method is used to obtain the characteristic paramerers of projectiles dispersion considering the error factors of system parameters and the state parameters of projectile at muzzle. The probability distribution of projectiles dispersion is obtained by using the the maximum entropy method. The test examples show that the results obtained by the SGNI method are in good agreement with those obtained by Monte Carlo method, and verify its effectiveness. In addition, an engineering example of 155 mm gun-howitzer is ananlyzed, and the the relation between single state parameter error and multi-state parameter error and the projectiles dispersionis established, which can be provided as reference for the overall design cosidering the dispersion of projectiles. [ABSTRACT FROM AUTHOR]

In order to explore the mechanism of how bore damage leads to the decrease in firing accuracy and the rise in the ratio of elliptical shot holes, eventually leading to the end of a barrel life, the thermo-mechanical coupling finite element analysis (FEA) models of barrels with bore damage at 4 life stages, including undamaged barrel, middle-early life barrel, mid-life barrel, and end-of-life barrel，are established based on barrel life tests. Uniform design method is used to design the simulation test of interior ballistics process influenced by random factors of ammunition. The response values of muzzle disturbances of differently damaged barrels were acquired in the simulation test. The simulated results are in well agreement with the experimental data. The response surface equation for muzzle disturbance for taking ammunition random factors as independent variable and the rules of how ammunition random factors influence the muzzle disturbances of differently damaged barrels are obtained by using the partial least-squares regression method based on cubic B-spline curve and the uniform design-response surface method. The simulated and analyzed results show that the contribution of each ammunition random factor to the muzzle disturbances of differently damaged barrels is unequal. In order to reduce the muzzle disturbances of barrels in its later lifetime, the mass eccentricity of bullet and the initial yield strength of jacket material should be decreased, and the cylindrical diameter and charge weight should be moderate. [ABSTRACT FROM AUTHOR]

The time-based distribution of vibration angular velocity of a barrel excited by the road irregularity, etc. and the relationship between it and angular error process of the barrel were analyzed in the context of high-speed gun firing on the move. A method to derive the angular velocity process of barrel was proposed based on mean square derivative, and the random cut-through characteristics of location-speed complex firing gate was analyzed. The simulation results show that complex firing gate, compared to simple firing gate, has the better indicators of random cut-through characteristics. [ABSTRACT FROM AUTHOR]

During the process between launch and water-exit, sub-launched missile will suffer wave forces, and the wave forces will affect the missile water trajectory parameters to a considerable degree. A random wave model was built using the Pierson-Moscoswitz spectrum and the SWOP direction distributing function, furthermore, equations for calculating wave forces were derived in reference of the section-cutting theory. According to the characteristics of the wave randomness, a series of statistical simulation were carried out by using the Monte Carlo like method. The rules of wave effect to the maximum parameter deviations of the uncontrolled ballistics with the variation of depth were obtained, and maximum ballistics parameter deviations of different sea conditions and wave angles were given, with the changing law described. The simulation method and results have a certain reference value for engineering studies. [ABSTRACT FROM AUTHOR]