In recent years,data-driven methods have received extensive attention and research,and data-driven provides a new research paradigm for the development of internal ballistics,which has a broad application prospect and development potential. This paper summarizes the relevant research results of data-driven methods in the field of internal ballistics in recent years,and mainly introduces the data-driven internal ballistic modelling technique and the data-driven internal ballistic performance optimization method. The paper also discusses the challenges faced by the related research and points out the directions worthy of further research in the future.

In order to deeply study the auto-initiation phenomenon of rotating detonation of high-temperature hydrogen-rich gas,the experimental study was carried out. The influence of equivalent ratio on the propagation characteristics of high-temperature hydrogen-rich gas rotational-detonation-wave was explored by analyzing the typical characteristic-parameters,and the equivalence-ratio range of the successful auto-initiation of high-temperature hydrogen-rich gas to form a rotational detonation wave was obtained,and the influence of equivalence ratio on the self-initiation delay time was analyzed. The results show that the intensity of the initial rotational detonation wave formed by auto-initiation is weak,and the propagation direction and propagation mode will change. However,through the self-adjustment of the rotational detonation,the stable self-sustaining propagation of the rotational detonation can be realized finally. While the flow rate of pre-fired oxygen is about 8 g/s and the air flow-rate is 270 g/s,within the equivalence-ratio range of 0.85-1.98,the high-temperature hydrogen-rich gas can form a stable rotational detonation wave through self-detonation. When the equivalence ratio is greater than 1.52,the rotational detonation wave is in a single-wave mode,and with the decrease of the equivalence ratio,it changes to a mixed mode,that is,under the same working condition,the single-wave,dual-wave mode and single/double-wave transition mode appear irregularly alternately. When the equivalence-ratio decreases to about 0.96,the rotational detonation wave presents a stable two-wave mode,and with the increase of the equivalence ratio,the auto-initiation delay time decreases from 138 ms to 106 ms. The propagation velocity of the rotational detonation wave increases first and then decreases with the increase of the equivalence ratio. The maximum value of the wave velocity occurs when the equivalence ratio is 1.33,and the wave velocity is 1 278 m/s.

To improve the propulsion safety of large-caliber solid propellant guns,the ignition system usually includes a primer and a flash tube in the axis of chamber. The combustion and flow of ignition propellant can be illustrated as a one-dimensional two-phase flow model. Combined with the one-dimensional two-phase model of main charge,the double one-dimensional two-phase model can be established for the simulation of interior ballistic process. Under a certain charge condition, the stress and fragmentation characteristics of the propellant particles were numerically simulated with the experimental stress and fragmentation function of the propellant particles in the bore. The simulation results show that the degree of fragmentation increases from 2.184 to 2.781,with an increase of 27.3%,as the mass of propellant in flash tube increases from 90 g to 110 g. The degree of fragmentation decreases from 2.487 to 1.35,with a decrease of 45.7%,as the length of the flash tube increases from 0.3 m to 0.38 m. The degree of fragmentation decreases from 2.487 to 1.997,with a decrease of 19.7%,as the diameter of the flash tube increases from 30 mm to 35 mm. The increase of mass of propellant in flash tube will lead to the increase of fragmentation in the charge bed,and the increase of the length or diameter of the flash tube will reduce the charging density of propellant in the flash tube,resulting in the decrease of fragmentation in the charge bed.

In the context of non-rolling control missile testing engineering,an optimization scheme was proposed for the placement of trajectory tracking positions to improve the accuracy of inconsistency correction in trajectory tracking positions without rolling control,taking the multi-beam radar measurement system as an example. Firstly,based on the tracking location information obtained from external measurement data,the correction amount of the tracking location was calculated by using measurement data from optical equipment or telemetry equipment to calculate the center position parameters of the missile inertial-navigation-platform. Secondly,the inconsistency correction error of the non-rolling control missile tracking part was analyzed by applying the principle of error transmission,and a method was proposed to improve the accuracy of inconsistency correction of the non-rolling control missile tracking part by deploying two tracking parts. Then,the influencing factors of the non-rolling control missile on the accuracy of inconsistent correction of the tracking position were separated. On this basis,the angle and distance of the tracking position were optimized to reduce the contribution of the non-rolling control missile to the correction error. Finally,simulation experiments were carried out by taking the optimization of two tracking-point layouts as examples. The results show that the proposed optimization scheme for tracking point layouts effectively improves the accuracy of tracking-point inconsistency correction in the background of non-rolling control missile,verifying the effectiveness of the optimization scheme.

In order to solve the problem of initial conditions for the numerical-solution of the differential equations of rotating-projectile rigid-body trajectory,the rigid-body dynamics theory was applied to analyze the nutation and precession motion at the initial moment of trajectory. The range of values for the initial nutation-angle and initial precession-angle of the projectile moving around the center of mass was provided. By establishing the trajectory coordinate-system,the transformation relationship between the initial velocity azimuth angle and the initial projectile-axis elevation angle,with the initial nutation angle and initial precession angle,was derived. While the initial nutation-angle and the initial precession-angle are not zero,the initial elevation-angle of projectile axis is not equal to the firing angle,and the initial azimuth-angle of the projectile axis is also not equal to the initial velocity azimuth angle. The 155 mm gun-howitzer projectiles with bottom concave was taken as an example for simulation research. The result shows that the initial nutation angle has an impact on the drift,as well as the nutation and precession laws in its motion around the mass center. The initial conditions and values range provided for the numerical solution of the trajectory can be used for numerical solution of the differential equations of rotating-projectile rigid-body trajectory.

In order to study the tail-fin opening characteristics of the image terminal-guided-projectile,according to the structure characteristics and action principle of tail-fin,the movement process of the piston after starting and the rotation process of tail-fin were studied,which were coupled with the bore process and the after-effect process of the terminal guided projectile. The numerical simulation was carried out for the certain image terminal-guided-projectile. The pressure of projectile base and cylinder,displacement and velocity of projectile,displacement of piston,opening angle of fin and gas resistance were obtained. The results show that the relative errors of maximum pressure on the base,muzzle velocity,tail opening position and tail-fin opening angle are 3.2%,0.7%,4.7% and 5.7% respectively,which are within the allowable range. The related simulation curves are consistent with the actual change law,verifying the rationality of the model. On this basis,the influence of charge and pore diameter on tail-fin opening characteristics of image terminal-guided-projectile was analyzed from the perspective of equipment production and firing use,and the specific guidance was given. The research results can provide theoretical and data support for structure optimization design,strength check and abnormal mechanism research of the tail structure of the image terminal-guided-projectile,and also provide reference for development and use of other new-type cylinder-opening tail-fin projectiles.

Bearing-only target tracking estimates distance and velocity of target by using only line-of-sight elevation and azimuth angles relative to observation station. To solve the problem of insufficient observability of relative distance,the corresponding improvement methods were proposed for three cases. ①For stationary targets with known initial-relative-distance,real-time distance can be calculated by using the velocity of observation station. ②When targets move at constant velocity or initial-distance errors are significant,observability can be enhanced through specific maneuvers by the observation station. ③If the relative altitude between the station and target is known,sufficient observability allows accurate distance estimation even for maneuvering targets. Simulations on stationary target,constant-velocity target and maneuvering targets reveal that the first method's error depends on initial value accuracy,while the second method's error is influenced by maneuver strategy and acceleration,causing a mean relative distance error of 5.26 m under designed conditions. For the third method,incorporating target maneuvers and measurement noise,Monte-Carlo simulations show root mean square errors(RMSE)of 0.81 m for relative distance and 0.95 m/s for distance rate,demonstrating robustness under complex cases.

The complexity and changeability of modem air-combat conlrontation makes air-combatdecisions fuzzy and changeable. Elfeelive trajectory prediction can greally improve the accuraey oldecision-making. Aiming at the characteristies of complex time series in air-combat trajectory prediction , atrajeetory prediction method integrating short-time Fourier transform( STFT ) and multi-stream transformernetwork was proposed to improve the accuraey of predicting air-combat maneuver trajectory. During air.combat maneuvers, the trajectory of aireralt changes frequently and complexly. Therefore , the trajectorydata were first preprocessed by high-order difference to eliminate noise and relain the spatiotemporalcharacteristies of trajectory. Subsequently,the short-time Fourier transform was used to extraet frequency-domain features of the preprocessed trajectory and analyze the dynamic changes of the trajectory. In orderto belter capture the dilerenees between position trajeetory and allilude trajectory ,a trajectory decouplingstrategy was designed to process these two types of trajectories separately. Then,the transformer nelworkbased on the multi-stream dynamic altention mechanism was used to process these spatiotemporafeatures ,thereby capluring the deep dependencies in the flight trajeetory. The network weights multiple data streams through multi-head attention mechanism, enhaneing the model's ability to capture the spaliotemporal dependeneies of dilerent data streams. Experimental results show that compared totraditional prediction methods,the proposed method has a 3.88%6 improvement in prediction accuracy. Thecombination of S'TF'T and multi-stream transformer elfeelively improves the predietion aceuraey of complexair-combat maneuver trajectory , verilying its applicability in high-precision air-combat scene prediction.

The downwash phenomenon of canard missile at low speed was studied by numerical calculation method and PIV experiment. The aerodynamic parameters and flow field of canard-shaped missile were calculated and analyzed under the condition of free-stream Mach number of 0.03(10 m/s)and 0.1(34 m/s). The results show that the downwash phenomenon of the canard missile is mainly affected by the shedding vortex of the canard with the downwash flow on the downstream flow field at low speed. A symmetrical effect is generated without the rudder deflection angle. In addition,the influence of the downwash phenomenon on the roll characteristics of the whole missile was explored when the canard was rolled(horizontal canard differential deflection). It was found that the roll reverse effect occurred. The main reason is that,the shedding vortex at the trailing edge of the horizontal canard rudder is asymmetric when the horizontal canard rudder is differentially deflected,so the downstream flow field is also asymmetric. That is,the shedding vortex of the canard rudder will interact with the vortex attached to the missile body and the tail,so that the area of the low-pressure zone above the two horizontal tails is asymmetric,and the normal force provided is not equal,and finally the tail produces a rolling moment opposite to the canard rudder control direction. With the increase of the attack angle,the reverse rolling moment generated by the tail fin is gradually greater than the forward rolling moment provided by the canard,leading to the rolling effect.

To study the influence of fragment shape,mass and other factors on the velocity attenuation law of prefabricated fragments in the flight process,the flying velocity test was conducted on spherical fragments,cuboid fragments and cuboid fragments recycled from static explosion tests using 25 mm ballistic-gun. Among them,the diameters of the spherical fragments are 7 mm and 8 mm respectively,and the masses are 3.9 g and 4.7 g respectively; the size of the cuboid fragment is 8 mm×8 mm×7.05 mm,and the mass is 7.94 g. Using Doppler radar velocity-measurement technology,the real-time velocity data of fragments during flight were measured,and the variation law of fragment velocity with time was analyzed. The variation law of fragment velocity with displacement was obtained by numerical analysis method. Finally,the fragment velocity-attenuation-coefficient,the relationship between the velocity attenuation coefficient of spherical and cuboid fragments and the Mach number(Ma)were obtained through data fitting. For spherical fragments,the velocity attenuation coefficient shows a decreasing trend with the increase of fragment radius. The velocity attenuation coefficients of 8mm spherical fragments were compared with that of 8 mm×8 mm×7.05 mm cuboid fragments. The result shows that the masses of the two types of fragments are significantly different,but the average velocity-attenuation-coefficients are close. Within the initial velocity range of 1 300-2 100 m/s,compared to cuboid regular fragments,the average velocity-attenuation-coefficient of cuboid fragments recovered from static explosion experiments is larger,indicating that they experience greater air resistance and faster velocity attenuation during flight in the air. The shape of the cuboid fragments recycled from the static explosion test is closer to that of fragments generated after the actual warhead explosion,and the test result has greater reference value for the design and power evaluation of the warhead.

To study the influence of thickness on dynamic response and energy-absorption characteristics of foamed concrete(FC)under explosion-load impact,the numerical calculation of anti-explosion of FC under 0.8 m/kg^1/3 ratio-detonation-distance and 0-30 mm thickness was carried out by using finite element software. Subsequently,the anti-explosion tests of FC with thickness of 0 mm,10 mm,20 mm and 30 mm,were carried out to verify the accuracy of the numerical calculation. Through numerical calculation,the damage form and energy-dissipation mechanism of FC under the impact of explosion-load were studied,and the ability of FC to absorb explosion-wave energy was quantitatively analyzed,and the law of the energy absorption characteristics of FC and the deformation response of aluminum alloy plate on the back influenced by the change of thickness of FC was obtained,and the corresponding engineering-calculation-model was derived. The results show that,the size of the FC crushing zone gradually shrinks with the increase of thickness. The FC crushing-zone only accounts for 2.9% of the overall volume when the thickness is 30 mm. FC can effectively absorb and dissipate the energy of explosion wave,and its energy-absorption capacity increases with the increase of thickness. The foam concrete with thickness of 5-30 mm can absorb 42.8%-91.9% of explosion wave energy respectively. The displacement response of aluminum alloy backplane steadily shrinks as FC thickness increases. While the thickness of FC is 30 mm,the displacement response of the center of the aluminum alloy backplane drops to 3.2 mm,which is only 12.6% of that without FC.

In order to evaluate the damage effect of block charges with different masses on the surface of concrete pier body,the damage characteristics of the concrete pier under the action of contact explosion were studied by numerical simulation,and the damage effect of the concrete pier body was evaluated by the equal damage curve,and the characteristics of the damage area of the top surface,side and side edge of the pier body under the action of contact explosion were obtained,and then the influence of charge quality and placement position on the damage effect of pier body was revealed. By establishing the calculation model of vulnerable volume,the variation curves of the remaining volume of concrete pier body with the charge mass under the action of contact explosion on the top surface,side and side edge were obtained. On this basis,the block charge with different masses was compared in 8 different positions on the concrete pier body during contact explosion,and the number of large fragments and the maximum fragment volume after the explosion were studied. The result shows that the shape of the damage area on the top surface and side of the concrete pier is approximately circular,and its center coincides with the center of the top surface. The shape of the damage area on the side edge is approximately elliptical. When the charge explodes in contact with the top surface,side and side edges,the damage effect at the center position is the best. When the charge mass is 1-3 kg,the damage effect of the explosive exploding at the geometric center of the top surface of concrete pier is the best. When the charge mass is greater than 3 kg,the damage effect of the explosion at the side geometric center is the best.

As a structure with excellent mechanical properties and multifunctional characteristics,the lattice structure has the characteristics of high strength,high energy absorption,and the like. In order to study the anti-penetration performance of the triply periodic minimal surface(TPMS)structure,we established lattice structure models of the Diamond and Gyroid types based on this structure. Silicon carbide ceramics were selected as the matrix material of TPMS structure,and its anti-penetration performance was studied by the ABAQUS finite element software. The research results show that under low-speed penetration,the Diamond structure significantly improves energy absorption,while the asymmetrical forces generated during impact and the erosion of the projectile in the Gyroid structure can effectively change the penetration angle. Aiming at Gyroid structure,finite element simulation was carried out under different working conditions,such as different impact points,different incident angles and increasing target thickness,and the influence of the change of incident angle on the anti-penetration performance of the Gyroid structure was analyzed. The result shows that the deflection degree of the ejection angle decreases first and then increases with the increase of the incident angle. In addition,when the projectile impacts the spiral surface of the concave Gyroid structure,the ejection angle of the projectile can be obviously changed. After increasing the thickness of the Gyroid structure by 50%,the change of bullet ejection-angle increases by 176.92%,and the absorbed energy increases by 78.26%. The Gyroid structure can effectively change the motion attitude of the projectile through its unique curved-surface structure. The research results provide certain reference significance for lightweight armor design.

In order to deeply research the wear mechanism of driving bands and explore the essence of the plastic deformation of driving bands,a comparison was made on the surface morphology,composition,microstructure and hardness of three driving-bands of 155 mm caliber artillery. The research results show that although the driving bands have different structural designs,compositional makeups and diverse service conditions,their microstructure distributions present common patterns after being in service,and their wear degrees are closely related to spatial positions. The wear on the non-driving side is generally lighter,and its microstructure is mainly equiaxed structure. Due to friction,fine-grained microstructure is generated at the top of the protruding part of driving band,while the internal microstructure morphology remains basically unchanged. The wear on the upper part of the driving side is the most serious,and the microstructure evolution presents a spatial distribution of fine-grained microstructure,fibrous microstructure,elongated microstructure and equiaxed microstructure from the surface to the inside. The wear degree at the bottom of the driving side is lower than that of the upper part. During the working process of the driving band,the deformation is concentrated on the surface,and the internal microstructure morphology above 200 μm from the surface hardly changes. The hardness analysis shows that the hardness on the non-driving side is similar to that inside the driving band,while both the upper part of the protruding position of the driving band and the upper part of the driving side present a "soft-hard" structure. Among them,the hardness of the fine-grained microstructure is the lowest; the hardness of the fibrous microstructure is the highest; the hardness of the equiaxed microstructure is in the middle. Among the three driving-bands,the wear of H96-2 is the most serious,while wear of H96-1 is the least.

In order to accurately calculate the recoil efficiency of a certain aircraft gun with multi-row oblique-side-holes muzzle-brakes,the numerical simulation on muzzle flow-field was carried out,considering the effect of projectile on propellant gas expansion and the acceleration effect of oblique-side-holes on propellant gas. The correctness of this numerical simulation method was verified by comparing the numerical simulation results of the muzzle flow field of a 12.7mm weapon with experimental results. The two-phase-flow internal-ballistic model of 30 mm aircraft gun was calculated numerically,and the flow state in the bore while the projectile reaching the bore position was obtained under the initial condition.The three-dimensional N-S equations of the muzzle flow-field were established,taking into account the interaction between the projectile and the propellant gas. A three-dimensional moving-grid method combining a polyhedral mesh for the stationary region and a hexahedral structured mesh for the moving region was adopted to numerically simulate the three-dimensional transient flow of the propellant gas when the projectile passes through each row of oblique-side-holes,which was compared with the case without considering the projectile motion. The results show that the oblique-side-holes can introduce high-pressure propellant gas into the barrel and generate supersonic airflow from the oblique rear,thereby producing a large recoil impulse. The recoil efficiency reaches 38.4%. The projectile impedes the expansion of propellant gas,resulting in stronger conical oblique shock waves at the oblique-side-holes. As a result,more propellant gas is ejected from the oblique-side-holes,increasing the recoil impulse. Therefore,projectile motion must be considered in numerical simulations of this type of muzzle brake. This research provides reference for the design of new multi-row oblique-side-holes muzzle-brakes and the dynamic matching between cannons and aircraft.