点火过程是内弹道的初始阶段,但由于点火过程的复杂性以及点火机理仍然不完善,点火过程始终不能与内弹道有机结合,使得目前工程上的内弹道计算只能忽略点火过程而直接选择点火压强作为计算初始点。以零维内弹道理论为基础,建立了点火过程3个阶段,即点火诱导期、火焰传播期和充气期的简化理论模型,可以与零维内弹道有机结合,从而完成了内弹道从环境压强(而不是点火压强)开始计算的完整过程。通过实例计算与验证,该模型能够很好展示在点火阶段燃烧室压强的建立过程,并可以计算得到点火延迟时间、火焰传播时间、点火药流量等点火参数,具有较高的预示精度,满足工程计算要求。研究表明,建立的点火过程理论模型与传统零维内弹道一样计算简便快捷,并具有较好精度的工程应用化特点。研究结果对于完善固体火箭发动机内弹道理论、提高固体火箭发动机内弹道预示精度,均具有重要的实际应用意义。由于采用了简化的点火过程理论模型,该结果不能直接用于点火性能的研究,只能用于零维内弹道性能的预估与计算。

During the electromagnetic launching process,the high speed sliding electrical contact about armature-rail is closely related to the accuracy of the rail spacing. Accurate measurement about the rail spacing can effectively guide the design of armature and researching for the matching about armature-rail. According to the cross-sectional,irregularly shaped characteristics,and the changing shape of the railgun. An high-precision measurement method for spacing size was proposed based on the angular bisector characteristic. In this method,the spatial position of two rails was divided into two segments that interest at a certain degree. The angular bisector was adopted as the measurement reference,and a measurement points were taken. The perpendicular lines of the two rails were drawn through the measurement point. The line connecting the two perpendicular feet was defined as the orbital spacing value. Through prototype design,comprehensive system error analysis,and comparative verification,a certain caliber railgun spacing engineering measurement was carried out. The results show that the measurement error is ≤0.05 mm,which satisfies the accuracy requirements. By obtaining accurate data of the rail spacing,an indispensable measurement method can be provided for numerical modeling,assembly process,and performance testing about electromagnetic launch devices.Thereby promoting the engineering application of railgun weapons.

Ballistics is one of the foundational disciplines in weapons science and technology,closely related to the development of weapons technology. With the rise and development of intelligent projectiles and rockets,the theory and technology of intelligent ballistics will be a major direction for the future development of exterior ballistics. Nevertheless,how to understand the concept,connotation,and functions of intelligent ballistics,as well as its differences from existing projectiles and rockets in terms of flight trajectories,the key technologies it relies on,the challenges involved,and the issues that should be considered for the subsequent development,are still under discussion. Based on the theory and technology of exterior ballistics and focusing on the future development of exterior ballistics,this article tends to analyze and organize the aforementioned issues with the aim of providing assistance for the future development of intelligent ballistics theory and technology. It should be noted that the development of intelligent ballistics theory and technology has introduced numerous new problems,concepts,terminologies and technologies for exterior ballistics,which require continuous exploration,refinement,and gradual perfection by researchers in the field of exterior ballistics through ongoing research. This article merely serves as a starting point,hoping to inspire more researchers in the field of exterior ballistics to engage in this area of study and gradually develop a theoretical framework.

From the development trend of modern artillery and ammunition technology,the problems faced by the internal ballistics of artillery were analyzed. The development direction of internal ballistics theory and technology is mainly reflected in three aspects. The first aspect is to improve the combat effectiveness of conventional solid propellant artillery. The second aspect is to develop internal ballistics theory and control technology that is matched with the launch methods of special ammunition such as guided munitions. The third aspect is to study the internal ballistic theory and control technology of new energy artillery. On this basis,combined with the research status at home and abroad,several key issues were reviewed,proposing research strategies.

In order to overcome the question of large fluctuation of trajectory tracking accuracy due to complex external unknown interference in the trajectory tracking control process of six-freedom-degree quad-rotor UAV,a new-type cascaded double-closed-loop control strategy was proposed for velocity error,and position and attitude error. Firstly,the model predictive control(MPC)was used to project the velocity closed-loop controller,and the sparrow search algorithm(SSA)was applied to the rolling optimization process of MPC to obtain the feasible solution due to the fast convergence and strong robustness. In order to solve the large computation in MPC,sliding mode control(SMC)was used to design the dynamic controller according to position and attitude respectively. SMC is insensitive to external interference,robust and does not need accurate modeling,thus solving the problems of external uncertain interference and difficulty in accurately modeling UAV. The saturation function was used to replace the symbolic function to make the input of the actual system continuous,thus effectively reducing the high-frequency chattering phenomenon in SMC. Finally,the stability of the SSA-MPC controller was proved by Lyapunov stability theory. By the proposed method,the six-freedom-degree quad-rotor UAV can achieve high-precision trajectory tracking control under complex external unknown interference and uncertain parameters,and the trajectory tracking accuracy is obviously better than the UAV control system composed of traditional single controller. The proposed controller is effective for the trajectory tracking control of quad-rotor UAV under complex external unknown interference.

Experimental study of two tandem cylinders entering the water obliquely was carried out based on high-speed camera in this paper. Cavitation evolution characteristics and movement characteristics of the tandem cylinders were analyzed. The results show that when the time interval is 3.5ms,cylinder Ⅱ(the front cylinder)enters the cavity of cylinderⅠ(the later cylinder)after entering the water,and collides with cylinderⅠ. According to the principle of independent expansion,cylinderⅠundergoes instantaneous acceleration after being impacted,resulting in rapid expansion of cavity in the cross-section at the impact location,forming a nested cavity. The collision disrupts the stability of two cylinders,causing them to flip over in the water. When the time interval increases to 10.2-31.8 ms,cylinder Ⅱ enters the cavity of cylinderⅠafter entering water without colisding with the cylinderⅠ. Cylinder Ⅱ enters water again after penetrating the cavity wall of cylinderⅠ. The resistance to the motion of cylinder Ⅱ in the cavity is significantly lower than that in water,so cylinder Ⅱ has good speed storage performance. When the time interval is 48.2 ms,the tail of the cavity of cylinderⅠdrifts up significantly with the effect of buoyancy. The repulsion between the cavity walls of two cylinders causes the trajectory of cylinder Ⅱ to shift under pressure,and cylinder Ⅱ does not enter the cavity of cylinderⅠafter entering the water. The movement characteristics of the cylinder Ⅱ after entering the water are similar to that of a single cylinder,indicating that the disturbance of the flow field after the cylinderⅠenters the water has little effect on the cylinder Ⅱ. However,as the cylinders move downward,the interaction between the cavity of cylinderⅠand that of cylinder Ⅱ affects the attitude of the cylinder Ⅱ moving in the water.

According to the demand of axial cold launch,an axial cold ejection device using high-pressure nitrogen as ejection energy was designed to avoid the pollution of the internal space of the platform. The structure composition,working principle and main design points of the axial cold ejection system were introduced. By using the ideal gas equation of state,mass and energy conservation equation and aerodynamics,the mathematical models were established for the high-pressure chamber,low-pressure chamber,valve port gas flow,and missile motion of the axial cold ejection system. In order to improve the separation speed and reduce the overload peak,based on the established mathematical models and the internal ballistics structural-parameters,VB language was used to program. Through simulation calculation and analysis,the main structural parameters of the ejection system such as cylinder initial pressure,volume,initial volume of low-pressure chamber,electromagnetic valve orifice,natural frequency,damping ratio and piston diameter,were studied to determine the impact on missile separation speed and launch overload. The influence of various structural-parameters change on the missile separation parameters was found,and the mechanism of the influence laws was analyzed. This study provides a theoretical basis for the optimization of the structural parameters of ejection system,and provides a theoretical reference and basis for the internal ballistics design of the same type of axial cold ejection launcher.

The issue of abnormal high initial-pressure inside the launch tube in a small-scale ejector was discussed. A calculation method based on a zero-dimensional internal-ballistics model was proposed,considering the combustion heat-release reaction of the rich gas,and the method has the advantages of simple principles,small calculation amount and fast calculation speed. A calculation program was developed using the Matlab. The effectiveness and accuracy of the numerical model were validated by comparing with ejection test results. Based on the above research,the phenomena of secondary combustion in the launch tube were further studied. The study shows that the time-curves of the pressure of launch tube and the acceleration of missile exhibit obvious double-peak effects whether secondary combustion occurs or not. Additionally,the secondary-combustion effect not only significantly increases the peak value of the first peak but also leads to a decrease in the peak value of the second peak. Furthermore,a sharp drop of pressure in the launch tube to a low value occurs after the peak value of the first peak,and the secondary-combustion effect also significantly affects the ejection velocity and the missile ejection-time. Further research shows that by increasing the initial volume of the launch tube and reducing the rich gas content,the effect of secondary combustion on the low-pressure chamber pressure and missile acceleration can be reduced. This study provides theoretical support for the design of internal ballistics in ejector system,and has a certain degree of universality and reference value.

The inflation process of parachute is the most critical step during the landing of the Mars probe. The model of computational fluid dynamics(CFD)and structural dynamics was built,considering low atmospheric-density and supersonic flow. The flow field was solved by using compressible flow-field model,and the structural dynamics was analyzed by using multi-node mass damped spring model of parachute system. The flow-field of the parachute was calculated,and the pressure field of canopy surface for the previous time step was imported to the multi-node mass damped spring model of parachute system. The canopy shape of the next time step was obtained,and the parachute shape and the flow field were obtained during the opening process. The test results and calculation results were analyzed comparatively,and the parachute inflation process was simulated under this condition. The numerical results are well consistent with the experiential results,so the mathematical model used is reliable. The results show that there is obvious vibration after the parachute-opening dynamic-load reaches the peak value,and the vibration frequency is only related to its own characteristics; the speed of the canopy opening is slow at first and then fast; under the same initial-speed,the peak value of the parachute-opening dynamic-load increases with the increase of atmospheric density; under the same initial dynamic-pressure,the peak value of the parachute-opening dynamic-load decreases with the increase of atmospheric density.

To investigate the dynamic response characteristics of penetration warhead under impact load,the simulation of warhead penetrating into a semi-infinite concrete target was conducted using the projectile-target separation method. The dynamic response of the warhead under different charge and shell head-curve-ratios,velocities,and sizes was analyzed. The results indicate that the deceleration peak of charge is higher than that of warhead shell. The deceleration peaks and deformation of the charge are positively correlated with the head curve ratio of charge. The deformation of the charge caused by stress wave is primarily concentrated on its end face and at the transition between the head and cylinder section. Increasing the head curve ratio(CRH_S)of the warhead shell reduces deceleration peaks for both the shell and charge,as well as their maximum overload difference. Specifically,the maximum plastic strain of the charge at CRH_S=4 is about 29% of that at CRH_S=2,with a significant reduction in high strain area. The initial velocity of penetration mainly affects the overload amplitude. Furthermore,an increase in initial velocity results in higher overload and plastic deformation for both the shell and charge. Overload,penetration depth and stress amplitude adhere to similarity laws for different warhead-sizes,without considering factors such as concrete aggregate size and strain rate. However,larger warhead size results in more severe plastic-deformation of charge.

As an important branch of electromagnetic launch technology,electromagnetic rail launch has significant advantages such as high launch speed and adjustable launch speed,and is regarded as one of the disruptive technologies that will change the style of future warfare. At present,electromagnetic rail launch technology still faces key bottlenecks such as low firing accuracy and short device life. These are closely related to the complex multi-domain coupled electrical,magnetic,thermal and force launch dynamics behavior involved in electromagnetic rail launcher. However,there is a lack of mature theoretical methods and technical tools for the analysis of system dynamics of electromagnetic rail launcher under extreme impact conditions at home and abroad. In response to the above situation,the corresponding research directions and needs comprehensive with recent domestic and international research progress in the dynamics theory and design methods of electromagnetic rail launcher from the aspects of dynamics modelling,performance prediction and optimization design was presented in this paper. With the engineering development of electromagnetic rail launcher,the dynamics modelling and simulation should consider the overall system factors of the launch environment,a rapid performance prediction and optimization design system for the launch dynamics of electromagnetic orbital launcher coupled with the launch environment should be developed,the basic scientific issues such as the vibration mechanism of electromagnetic orbital launcher coupled with the launch environment in multiple domains should be elucidated in details,and provides support for in-depth research on the dynamics and equipment development of electromagnetic rail launcher.

In order to study the influence of acoustic impedance difference on the flow field structure of detonation tube exit in jet environment,an axisymmetric model of the flow field inside and outside the detonation tube was established. The rhoReactingCentralFoam solver of the OpenFoam platform was used to couple the flow field inside and outside the detonation tube. Three free jet regions of argon,hydrogen and air mixture,and helium were constructed outside the tube. Combining with the simulation results of the static air outside the tube,the influence of the acoustic impedance difference of the medium inside and outside the tube on the detonation flow field structure was analyzed. The results show that the argon jet and the static air will form a reflected shock wave on the acoustic impedance discontinuity surface when the detonation wave overflows outside the tube. The helium jet forms a reflected rarefaction wave on the acoustic impedance discontinuity surface when the detonation wave overflows outside the tube. The hydrogen and air mixture jet has no effect on the process. The Mach disk formed in the argon jet and the static air is reduced to almost disappear. The slip line and the subsequent supersonic region encounter near the Mach disk. The Mach disks in the hydrogen-air mixture jet and the helium jet remain a certain size after decreasing. The slip line and the subsequent supersonic region encounter far away from the Mach disk. The acoustic impedance difference between the free jet and the explosive mixture causes the leading shock wave to deform and change its directivity. The curvature of the leading shock wave near the central axis in an argon jet decreases,and the leading shock wave in still air roughly presents a spherical wave shape. The leading shock wave in a hydrogen air mixture jet and a helium jet protrudes.

In order to achieve fast and accurate calculation of the exiting-water altitude of submarine launched missile,a model of ocean flow field and an exiting-water dynamics model of submarine launched missile were established in this paper. Based on which,the effect of cavitation phenomenon on the hydrodynamic characteristics of the missile was analyzed. The effects of missile velocity,ocean current velocity,wave height,and exiting-water phase on the missile exiting-water attitude were studied. The research results indicate that,the cavitation effect has a relatively minor impact on the missile attitude when the speed is less than 20 m/s during the exiting-water process. The action time of the wave forces on the missile is related to the launch velocity. The lower the missile velocity is,the more perturbation of the missile altitude is. The higher the ocean current velocity is,the more severe the disturbance to the missile attitude and the lateral deviation are. The wave height affects the amplitude of wave force and has a direct impact on the parameters of water outlet attitude. The larger the wave height,the greater the impact on the parameters of water outlet attitude. The initial phase and flow velocity of the outflow mainly affect the direction of motion of fluid particles,changing the additional inertial force of waves. The missile's outflow at the trough and peak positions has the greatest impact on the missile's attitude,and the wave node is between the two.

During the separation process of embedded-backward submunition,the bullet enters a semi-constrained state when the rear and middle hangings detach from the guideway. Therefore,the movement attitude of the bullet is significantly affected by the carrier vehicle. The contact collision between the hanging and the guideway,as well as the aerodynamic interference of the carrier vehicle on the bullet,have great influences on the separation process. In order to provide important theoretical support for the design of the submunition high-speed separation system and achieve safe separation of the submunition,a high-precision space-time numerical simulation security evaluation method of the high-speed separation for submunition were proposed. Based on the constructed aerodynamic response surface model and the variable-configuration variable-mass multibody dynamics model of the submunition,the multibody-aerodynamic fluid-structure coupling high-precision space-time numerical simulation platform for the variable-configuration variable-mass combination of the separation process for submunition was established. Different initial boundary conditions were applied to the fluid-structure coupling dynamics model and simulation was carried out to obtain the attitude parameter of the submunition separation process Then,the separation safety of the submunition dynamically evaluated,and the safety initial boundary conditions of the submunition separation was obtained. It can provide a quantitative design basis for formulating technical measures that are conducive to improving the safety of high-speed separation of submunition. Through simulation example and test,it is shown that the constructed high-precision space-time numerical simulation platform for high-speed separation of submunition has high accuracy and credibility. The research results provide important engineering value for the security design of high-speed separation for submunition.

To study the effect of heavy rainfall on the aerodynamic characteristics of gliding-guided projectiles,a model based on the Euler-Lagrange method with two-way momentum coupling,the Transition SST(shear stress transport turbulence model)and the MUSCL format with third-order accuracy were developed to calculate the aerodynamic properties of the projectiles under heavy rainfall. The results reveal that heavy rainfall creates an advective water film layer on the projectile surface,but the subsequent impact of raindrop particles on the surface results in craters forming and increasing surface roughness. The study shows that the rainstorm environment significantly impacts the lift and drag coefficients of the projectile,with a 27.39% increase in drag coefficient and an 18.09% decrease in lift coefficient observed when Ma=0.8 under a rainfall intensity of 2 200 mm/h. Additionally,the study shows that with an increase in rainfall intensity,the drag of the shell exhibits an initial increase,followed by a decrease,and then an increase again. However,this trend disappears as the projectile's flight speed increases while the lift coefficient decreases. These findings can aid in optimizing the performance of gliding-guided projectiles in adverse weather conditions. When the rain intensity remains unchanged and the projectile velocity reaches Ma=0.95,the drag coefficient increases by 32.29% and the lift coefficient decreases by 18.38%. When the projectile velocity reaches Ma=1.2,the drag coefficient increases by 21.76% and the lift coefficient decreases by 18.87%.

Cellular steel-tube-confined concrete(STCC)target has excellent anti-penetration ability and expandable performance. Based on finite analysis software ANSYS/LS-DYNA,the penetration process and anti-penetration mechanism of cellular STCC target normally penetrated by rigid projectiles were numerically simulated by using FEM/CSCM-SPH/HJC method. Compared with single-cell STCC targets and non-confined concrete target,the confinement effect of cellular steel-tube mainly reflects at the tunneling penetration stage and shows lateral confinement expansion of concrete at nose of projectiles. Compared with single-cell STCC target,surrounding cells of seven-cell cellular STCC target exert supporting on the steel tube in the impacted-cell. It restrains radial expansion of impacted concrete and bending deformation of steel tube,which can be treated as supplementary confinement of the surrounding cells. Compared with non-confined concrete target,it is the confinement of steel tube that improves the confining effect of concrete in the impacted cell,which enhances compressive strength and deformation performance of concrete in the impacted cell,and the penetration ability of the impacted cell is improved. Therefore,owing to confinement of the steel tube and supplementary confinement of the surrounding cells,the cellular STCC target exhibits excellent anti-penetration ability.

In order to study the damage effect of the near-field strong shock wave on the covered charge,the dimensional analysis method on the sympathetic detonation with covered plate was established theoretically. The shock initiation process of covered-pressed TNT was numerically simulated by nonlinear finite element program ANSYS/LS-DYNA. The influence of covered plate thickness,donor charge mass,length-diameter ratio of donor charge on the detonation distance during non-contact explosion was analyzed. The functional relationship between covered-plate thickness and sympathetic detonation distance was obtained by a non-linear least square method,as well as the functional relationship between donor charge mass and sympathetic detonation distance. The results show that the dimensional analysis results are in good agreement with the fitting formula,which fully demonstrates the validity and accuracy of the fitting formula. The calculated detonation distance of the non-contact explosion decreases with the increase of the covered-plate thickness. While the covered-plate thickness is less than 3 mm,the increase of the covered-plate thickness has a greater impact on the sympathetic detonation distance. While the thickness is greater than 3 mm,further increasing the covered-plate thickness has significantly smaller effect on increasing the shock initiation resistance of explosive. When the length-diameter ratio of the donor charge remaining constant,the detonation distance of the non-contact explosion is linear with the donor-charge radius,and cubic with the donor-charge mass. Under the donor-charge mass remains constant,the detonation distance of the non-contact explosion is the largest when the diameters of the donor-charge and the acceptor charge are equal.

In order to study the aerodynamic characteristics of the missiles with tail fins,simulation was conducted to study the unsteady flow-field of the missiles with rotating tail fins based on sliding mesh method. The numerical simulation method adopted in this paper was verified by the wind tunnel experimental results of army-navy finner(ANF)standard model. Taking a certain cross-shaped layout tail-fin missile as the research object,the variation laws and influencing mechanisms of various aerodynamic-characteristic-parameters at different Ma(Ma=0.9-2.0),attack angles(2 °,4 °),rotation speeds(π rad/s,2π rad/s,4π rad/s),and tail-fin inclination angles(0°,1°,2°),were analyzed. The calculation results show that the rotation speed has little effect on the longitudinal aerodynamic characteristics(drag,lift,pitch moment characteristics)of the missile,mainly affecting the roll characteristics and Magnus effect. The inclination angle of the tail fin has little effect on the lift characteristics parameters and pitch moment characteristics of the missile,mainly affecting the drag,roll characteristics and Magnus effect. The resistance characteristics parameters and lift characteristics parameters of the missile show periodic variation during missile rotating around its longitudinal axis(0°-360°),and the instantaneous coefficient of lift and drag is the smallest when the missile rotates to 45°. The body is the dominant factor in generating the resistance characteristic(about 85%). The contribution of the body and tail to the lift characteristics is basically about 50% each. Therefore,in the design process of the projectile and arrow,attention should be paid to the advantages and disadvantages of the fin cant angle and rotation speed,and a suitable oblique angle should be selected.

The eddy current braking machines have the advantages of no liquid leakage,no sealing required,and stable resistance. Compared with the more widely used permanent magnet eddy current braking machine,hybrid excitation eddy current braking machine replaces part of the permanent magnet with a coil an achieves better resistance characteristics. In this paper,two possible structure of hybrid excitation eddy current braking machines was compared. Based on magnetic circuit analysis and preliminary calculations,the structure with better resistance performance was selected. Equivalent magnetic circuit method was utilized to calculate the air gap magnetic field and subdomain models were adopted to consider effects of induced eddy current. Then,an equivalent subdomain model was established for calculating the resistance value of hybrid excitation eddy current braking machines. According to the requirements of a certain caliber artillery recoil,the main dimensional parameters of the braking machine were determined,and the preliminary design of the structural parameters of hybrid excitation eddy current braking machines was obtained. The analytical calculation results were verified by numerical calculation. Based on the working conditions when a certain caliber artillery is fired,the chamber force curve and recoil stroke function curve of complex feed mechanism were adopted as input conditions. A simulation model was established to analyze the electromagnetic damping force,recoil displacement and recoil velocity of hybrid excitation eddy current braking machine under strong impact load. Finally,the influence of different air gap widths and inner cylinder conductivity on electromagnetic damping force is analyzed. The results show that the smaller the air gap width is,the larger the electromagnetic damping force is. Meanwhile,higher conductivity of the inner cylinder will lead to the electromagnetic damping force showing a“saddle”type. The research provides a theoretical basis for the engineering application of the hybrid excitation-type eddy-current braking machine.

To improve the response capability of large vertical overturning equipment,a new type of gas hydraulic hybrid actuator was designed. A mathematical model for the movement and change of the "concave" grain combustion surface at different combustion stages and a numerical calculation model for the internal ballistic of the gas-liquid hybrid actuator were established. To verify the accuracy of the numerical model,product development and experimental research were carried out for the gas-liquid hybrid power device. Through the matching design of the combustion surface of the "concave" grain,rapid pressure building and stable output control of the flow rate at different combustion stages were achieved. The accuracy of the internal ballistic numerical model established in this article and the reliability of the hybrid actuator system design were verified. On this basis,the influence of the design parameters of the "concave" grain on the working performance of the actuator was analyzed. The calculation results show that the output flow rate of the actuator and the response time are mainly related to the initial combustion surface and the thickness of the flesh during the increased combustion stage of the "concave" grain,and the overall height of the grain determined the working time of the actuator system. Under the calculation conditions of this article,for every 10 mm increase in groove diameter and grain height,the response speed,average output flow rate,and working time of the actuator increase by about 0.09 s,13 L/min,and 0.2 s,respectively. The research results provide a new power source and internal ballistic design method for the rapid deployment of large vertical devices.

To study the mechanical response about rifling's steering side and band in engraving process,the motion,deformation of band and its mechanical mechanism during projectile engraving process were deduced based on the energy method,and the force relation between the rifling's steering side and band after engraving was analyzed according to the classical interior-ballistics theory,and the general expressions of the force on rifling's steering side during engraving process and after engraving were obtained. The influencing factors of the force on rifling's steering side were analyzed. Interior ballistics was simulated by using an elastic-plastic finite-element-method,and dynamic responses of the force on rifling's steering side were obtained under various operating conditions. The force on rifling's steering side,influence law of engraving velocity and angle of forcing cone were analyzed. The researches show that the force on rifling's steering side is positively correlated with engraving velocity and angle of forcing cone,and its trend of change is consistent with the bottom pressure of the projectile after engraving in. Within a certain range of velocity,the peak of the force on rifling's steering side during projectile engraving is much larger than that at the moment of maximum chamber-pressure,and the ratio of them shows a significant increasing trend as the engraving velocity increases. For the cased telescoped ammunition with longer free-travel-distance,the force is more complex in engraving process,so it's necessary to strengthen charge structure and optimize forcing cone to improve the barrel life. The calculation methods and conclusions mentioned can provide theoretical reference for projectile structure design and analysis of projectile-barrel matching.

Flight stability has a direct and significant effect on the retention ability and target attitude of explosively formed projectile(EFP),and then affects the penetration power of EFP after long distance flight. In order to obtain an EFP configuration with low resistance and flight stability,a single-tail skirt EFP for supersonic flight(Mach 4-7)was proposed. The effects of structural parameters(tail skirt angle 0°-25°,tail skirt length to total length ratio 0.2-0.7,length-diameter ratio 3-7,solid length-total length ratio 0.2-1)on aerodynamic parameters such as lift coefficient,drag coefficient and static stability reserve of EFP were studied numerically. The results show that lift coefficient and drag coefficient are positively correlated with tail skirt angle,tail skirt length and length-diameter ratio. Statically stable reserve is positively correlated with tail skirt angle and length-diameter ratio,and increases first and then decreases with the increase of tail skirt length. The solid length has almost no effect on the lift coefficient,drag coefficient and pressure center position of EFP,but the solid length affects the static stability reserve by changing the centroid position of EFP. The analysis shows that when the tail skirt angle is 20°,the ratio of the tail skirt length to total length is 0.265,the ratio of the solid length to total length is 0.755 and the length-diameter ratio is 5,the EFP structure of the single tail skirt has low resistance and good flight stability. The influence of Mach number and angle of attack on the lift resistance coefficient and static stability reserve of EFP was studied. The results show that the larger the Mach number,the smaller the resistance coefficient. The larger the angle of attack,the larger the resistance coefficient and the static stability reserve. The research results offer reference for the design of EFP warhead with high penetration performance from the perspective of aerodynamics.

The penetration test of 12.7 mm armor-piercing incendiary ammunition on a certain type of ceramic composite armor plate structure was carried out. The limit penetration velocity of the projectile to the composite armor plate and the damage pattern of the target plate was obtained. The finite element model of the projectile penetration of ceramic composite armor plate was established based on the smoothed particle hydrodynamics method in LS-DYNA. The finite element model was verified by comparing the maximum penetration velocity of the projectile,damage patterns and perforation size on the front side of the ceramic plate,deformation and damage on the back side of the composite target plate obtained from the experiment and numerical simulation. Then,the effect of the attack angle on the dynamic response of the projectile and the target plate in the penetration process was simulated and analyzed. The results show that,the penetration ability of the projectile to the ceramic composite armor plate is enhanced due to the decreasing of contact area between the head of projectile and target when the attack angle increasing from 0° to 6°. With the attack angle further increasing,the penetration ability of the projectile penetration ability decreases. It is resulted from the interaction the tail of projectile with the unbroken ceramic outside the central crushing area of the ceramic plate after the projectile penetrates the ceramic target plate due to the large deflection angle of the projectile. The interaction consumes part of its kinetic energy and leads to the decrease of its penetration ability. The energy absorbed by the ceramic is approximately 5 times that of the composite material layer,indicating that the attack angle mainly affects the energy absorption of the ceramic plate and consequently influences the penetration of the target plate.

In order to study the lethal effect of small-caliber prefabricated fragmentation warheads in terminal defense,finite element method was used to simulate the detonation of prefabricated fragmentation warheads. The dispersion characteristics of fragmentation under four detonation conditions:central detonation at the bottom of the charge,single-point off-center detonation,dual-point symmetrical detonation,and dual-point center-off-center detonation was studied. The average final velocity and average scattering angle of the prefabricated fragments,as well as the distribution ratio,under the four detonation conditions were obtained. The research results show that when the detonation position is located at the contral-bottom of the charge,the scattered final velocity of 71.7% of prefabricated fragments is between 300-800 m/s. The scattered final velocity of the prefabricated fragments is approximately 687.1 m/s,and about 91.7% of the fragments' scattering angle are distributed within ±45°. After changing the detonation position of the charge,the average scattered final velocity of the prefabricated fragments changes. The average scattered final velocity of the fragments decreased in average final velocity by approximately 1.2%-2.5%,as the off-center distance increased under single-point off-center detonation condition. For the dual-point detonation conditions,the average scattered final velocity of the prefabricated fragments showed a trend of decreasing-increasing-decreasing under dual-point detonation conditions. The average final velocity of fragments can be increased by about 5% when the eccentricity distance is increased appropriately. The average scattering angle of the fragments decreased with the increase of the off-center distance of the detonation position for the off-center detonation. Therefore,in order to enhance the damage capability of the warhead,the off-center distance of the detonation points can be appropriately increased for the dual-point detonation method,For the single-point detonation method,the off-center distance should be appropriately reduced. The research results provide reference for the design of prefabricated fragmentation warhead warheads.

Light composite armor is one of the key points modern armor protection system. In order to study the anti-penetration performance of ceramic/fiber composite targets with different ceramic thicknesses,ballistic test of 12.7 mm armor-piercing incendiary projectile penetrating aramid/SiC ceramic/ultra high molecular weight polyethylene fiber composite targets under the same working condition was carried out. The core and target plate were recovered after the test. Then,the crushing characteristics and failure modes of the core and ceramics were observed and analyzed. At the same time,the recovered projectile core and target fragments were screened and weighed,and the cumulative mass distribution of projectile core and ceramic fragments was analyzed. Thus,the anti-penetration performance of ceramic/fiber composite target was characterized. The results show that the head of the core is crushed into powder and the body is crushed into irregular fragments. While the remaining core is not broken and the fracture surface shows the characteristic of regular fracture. It is found that there are regular cleavage fracture characteristics in the remaining core by scanning electron microscope,which indicates that the main failure modes are brittle fracture and local plastic deformation under tensile stress caused by multiple fracture failures. The ceramic crushing form includes annular crack,radial crack and ceramic cone with cone angle generated by the two kinds of cracks interweave. The ceramic cone angle increases by about 11.67% for every increase of 1 mm in ceramic thickness. The ceramic crushing area is divided into crushing zone and crack zone. The crushing zone is the circular area on the target. The crushing area increases by about 11.13% for every increase of 1 mm in ceramic thickness. Based on the statistical analysis of projectile core and ceramic fragments,it is found that the cumulative mass distribution law of projectile core and ceramic fragments accords with the Rosin-Rammler power law distribution function model. With the increase of ceramic thickness,the average characteristic size λ decreases,and the fragmentation degree of projectile core and ceramic increases.

Large-caliber howitzers are mainly equipped with modular charge structures,which result in complex flow field. Based on the modular charge structure,a two-dimensional axisymmetric two-phase flow interior ballistic mathematical model for the combustion field partitioning inside the short-barrel gun was established. The MUSCL scheme was used to solve the model. A program was developed to numerically simulate the flow field inside the cannon barrel. The study primarily focused on the combustion process within the modular charge chamber and the influence of different rupture pressures on the combustion of the modular charge structure. The results indicate that the overall average error between simulation results and experimental data is approximately 7.42%,with a peak error of 0.72%. It shows that the established mathematical model and developed program can effectively simulate the firing process of the modular charge artillery. Furthermore,it is observed that the modular charge container hinders the transmission of flame waves. Prior to the rupture of the modular charge container,the flame wave and the pressure wave mainly flow inside the module,and there is less exchange with the outside material. Until the modular cartridge is broken,the powder particles move to the free space in the chamber with the pressure wave,and the flame wave and the pressure wave begin to transmit in the chamber. Moreover,as the rupture pressure of the modular charge container increases,the combustion of the module-loaded propellant chamber becomes more complete,and the pressure rise time becomes shorter. The ignition gas from the igniter diffuses into the surrounding area through the ignition hole,causing the temperature inside the chamber to gradually increase from the ignition hole and spread to the surrounding area,thus igniting the firing propellant.

To improve the aerodynamic ballistic performance of the gliding guided projectiles in the climbing phase and gliding phase and achieve significant range increasement,the gliding guided projectile with conventional fixed shape was designed with variable shape by combining the variable sweep and variable span of tail fins. Missile Datcom was used to calculate the aerodynamic parameters. The shape parameters of canards were adjusted with the span and sweep angle of tail fins deformation. Based on the NSGA-Ⅱ multi-objective optimization algorithm,the multi-objective optimization design of variable shape for the climbing phase and the gliding phase of the gliding guided shell was carried out. Then,the optimal shape schemes for each flight phase were finally obtained. In the climbing phase,the optimization objectives are the zero-lift drag coefficient and static stability margin of the projectile. While in the gliding phase,the optimization objectives are the lift-to-drag ratio and the maneuvering ratio of the projectile. The numerical simulation results show that the optimized variable shape scheme can significantly improve the aerodynamic and ballistic performances of the gliding guided projectile in each flight phase. The drag coefficient in the climbing phase is reduced by 13.3%,the lift-to-drag ratio in the gliding phase is increased by 36.1%. The optimized gliding guided projectile is table during the entire flight process,with good matching of stability,maneuverability,rudder deflection angle,and equilibrium angle of attack. Compared with the baseline fixed shape scheme,the range of the gliding guided shell with variable shape scheme under gliding control conditions is increased by 8.4%. The research provides a reference for the design of variable shape scheme of gliding guided projectile.

Addressing the challenge of controlling impact angle and time during the terminal guidance phase of gliding-guided projectiles,a scheme was proposed to simplify the guidance law design process and facilitate engineering applications. This scheme extends existing high-performance,non-time-critical guidance laws to accommodate time constraints. Based on a nonlinear guidance model and using the projectile's flight trajectory under existing guidance laws as a reference,the proposal divided the terminal guidance phase into two stages. In the first stage,the projectile flies under the extended guidance law,adjusting the reference trajectory's curvature and extending flight time to converge the impact time error to zero within a finite period. In the second stage,the original guidance law takes over until the target is hitted,ensuring compliance with miss distance and impact angle constraints. Extensive simulations were carried out under various conditions. The impact of design parameter ranges on the convergence performance of impact time error in the first stage was studied. The derivation of this extended scheme does not require an explicit expression of the existing guidance laws,offering a degree of universality. The results indicate that with appropriate parameter settings,the extended scheme can achieve impact time control on the basis of existing guidance laws,with smooth guidance commands and minimal required overload,meeting the operational requirements.

In order to expand the application scope of folding wing UAV and extend the information acquisition ability of underwater platform,an underwater vehicle scheme of carrying UAV for dry launch was proposed by combining the advantages of UUV and UAV. In order to better evaluate the feasibility of launching UAV on the sea,the computational fluid dynamics simulation software StarCCM+ was used to simulate the launching environment of UAV on the sea,and the floating and launching process of UAV was simulated in the simulation environment. The air-bag scheme and the propeller scheme were designed respectively by referencing foreign design experience,and the different sea-conditions,different structural-parameters and attitude parameters were simulated and evaluated,and finally the launching process was simulated under the sea conditions. The results show that the UAV carrier in the state of zero buoyancy underwater can float stably on the water surface under different sea-conditions by the air bag scheme and the propeller propulsion scheme. In terms of UAV launch,the difference between the maximum sinking distance of the air-bag scheme in still water and sea conditions is about 2.5%,and the consistency is better than the error level of the propeller scheme of 30%. The average maximum sinking-distance of the vehicle during the launch of UAV is 0.28 m,which is lower than 0.4 m of the propeller propulsion scheme. In a comprehensive comparison,the air-bag scheme is more stable and reliable.

Mines,improvised explosive devices and roadside bombs have become serious threat to vehicle-mounted howitzers(VMH),and the blast wave generated by mine explosion can also cause damage to the cab structure of VMH and endanger the life safety of crew. Because of the significant difference in the response of the shock wave generated by the mines explosion at different positions at the bottom of the cab,numerical simulation of the response process of the cab bottom of VMH under six explosion-shock conditions was carried out. ALE algorithm was used to establish models of soil,air and explosive,and Lagrange algorithm was used to establish the models of cab and chassis of VMH,and the fluid-solid coupling algorithm was used to calculate the propagation process of the explosion-shock wave,as well as the dynamic response of the cab of VMH in this process. The changes of shock-wave pressure,acceleration and velocity at the bottom plate of the passenger's foot position were analyzed,and the maximum shock-wave pressure,acceleration and velocity at the bottom plate of the passenger's foot position were obtained,and the damage to the cab structure under the worst-case operating conditions was analyzed. The simulation results show that the shock wave generated by the mine will make the cab floor produce greater acceleration and speed,and the cab structure will be damaged. In this case,the passengers will be injured. It is necessary to add a protective structure for the cab of VMH. The simulation results can provide reference for the design of cab protective-structure of VMH.

The engraving process of projectile accompanies the mechanical environment of strong impact,high overload,and high temperature. During this process,the homogeneous brass rotating band undergoes plastic deformation and damage destruction under the action of rifling land,resulting in the copper hanging on the inner surface of the barrel. With the widespread use of the concave hexagonal negative Poisson's ratio honeycomb structure(CHNPRHS),a novel CHNPRHS rotating band was proposed for the purpose of reducing the copper hanging phenomenon,taking advantage of the excellent load reduction and impact resistance of the structure. The finite element model of the rotating band engraving into the barrel was established. The deformation mode and mechanical properties of the CHNPRHS rotating band in the condition of positive propellant were studied. The research results show that the CHNPRHS rotating band satisfies the internal ballistic performance requirements during firing. While the movement of the projectile in the process of engraving is not significantly different from that of the traditional homogeneous brass rotating band. Due to the fact that the CHNPRHS rotating band undergoes three deformation stages of the elastic,plateau,and densification. There is slight damage and fracture on the surface of the rotating band,and it adheres well to the inner surface of the barrel. Compared with the conventional rotating band,the damage and energy consumption of the rotating band during engraving can be reduced by 76.9%. The CHNPRHS rotating band can decrease the occurrence of copper hanging on the inner surface of the barrel,and reduce the surface erosion of the barrel to some extent,thereby improving the service life of the barrel.