Ballistic Stability Research Articles

INFLUENCE FACTORS ON THE FORMATION OF MECHANICAL PROPERTIES AND STRUCTURE OF STEEL FOR MANUFACTURE OF RAILWAY AXES

The article investigated the features of the destruction and deformation of metal plates made of 30CrNi2Mo steel after ballistic tests. The peculiarity of the experiment was that during the test, the plates was additionally subjected to vibration at frequencies of 10 and 20 Hz. The perspective of the impact of vibration on the ballistic stability of plates has been revealed. After the experiment, through-holes of fragmentation and petal types with subsequent cracking were found in the static plates. Cracking propagates deep into the undeformed plate. The application of vibration showed a significant improvement in ballistic properties. When applying the combined test, a change in the resistance of the target was detected. Namely, the plastic component of the metal around the hole was increased and bullet fragments were found that remained on the surface of the plate after the test. It is shown that the further application of vibration is a promising direction for increasing the ballistic resistance of materials.

Experimental study on ballistic stability of truncated cone projectile in high-speed oblique water entry

In this paper, the high-speed photography technique was used to study the high-speed oblique water entry of truncated cone projectiles, and the effects of nose shape, projectile velocity and entry angle on the cavity and ballistic characteristics of oblique water entry were discussed. The experimental results show that the influence of nose shape on the oblique water entry cavity and ballistic characteristics is related to the nose wetted area. For the same type of projectile, with the increase of projectile velocity, the cavity size becomes larger at the same penetration displacement and the surface closure time gets longer. Moreover, with the increase of entry angle, the surface closure time decreases, the velocity attenuation gets faster, at the same penetration displacement the cavity opening length becomes shorter and the cavity asymmetry weakens. Additionally, the results indicate that the trajectory stability of the truncated cone projectile varies under different water entry velocities and attitude angles.

Trajectory deflection of noncircular cross-section projectile penetrating into metal targets

To analyze the trajectory deflection of a noncircular cross-section projectile penetrating into multiple metal targets, numerical simulations with different impact velocities, projectile tip height and charge geometry are conducted. The simulation model is established using the finite element software LS-DYNA and verified based on the experiment carried out by a single-stage light gas gun. The results show that the impact velocity significantly affects the trajectory deflection of noncircular cross-section projectile. Although the deflections may be different in direction, the magnitudes exhibit decreasing trends with the increasing impact velocity. Besides, the trajectory varies from downward deflection to upward deflection with the increase of projectile tip height, and changes significantly with the tip height ranging from 0.8mm to 1.1mm. Further, as the geometry profile of projectile remains unchanged, the ones with noncircular charge exhibit better ballistic stability as compared with the circular charge projectile. This is mainly related to the variation in projectile mass instead of the variation in moment of inertia.

Aerodynamic parameter calculation and ballistic stability research of special projectile

Based on the aerodynamic layout of special projectiles, a targeted aerodynamic parameter solution algorithm is built by a mechanical analysis model. The simulation software is used to analyze the ballistic stability. The results show that the aerodynamic layout with the center of gravity moving down is helpful to overcome the rolling interference in uncontrolled flight.

Effects of Lateral Flows on the Supercavitation and Hydrodynamic Characteristics of Underwater Series and Parallel High-Speed Projectiles

In this paper, the supercavitation of the parallel and tandem projectiles moving underwater with high-speed under the condition with/without lateral flows is numerically simulated by the volume of fraction (VOF) model. The motion of the projectiles was handled by the overlapping grid and six degrees of freedom (DOF) techniques. The supercavitation evolution and the hydrodynamic characteristics of the projectiles were analyzed for the parallel and tandem projectiles under different conditions. The results show that the cavity shape is symmetrical under the condition without lateral flows, but is no longer symmetrical under the conditions with lateral flows. The asymmetry of the cavity contour increases with the velocity of the lateral flow. For the parallel projectiles, the change trends of the axial velocity of projectile 1 and projectile 2 are nearly the same. The offset velocity of projectile 1 and projectile 2 increases with the increase in the velocity of the lateral flow. The deflection angle of projectile 1 decreases with the increase in the lateral flow velocity but that of projectile 2 increases with the increase in the lateral flow velocity. At t = 3.0 ms, the deflection angle of projectile 2 is up to 20° under the condition of the lateral flow velocity of 11.25%, while the deflection angle of projectile 1 and 2 under other conditions is in the range of 5°. For the tandem projectiles, the axial velocity of projectile 1 gradually decreases. The change trend of the axial velocity of projectile 2 at first is the same as that of projectile 1, and then the change is dependent on the velocity of the lateral flow. Under the condition of the lateral flow velocity with 11.25%Vp, projectile 2 cannot enter the cavity of the front projectile. The change trend of the axial velocity of projectile 2 is similar as but somewhat slower than that of projectile 1. For the parallel projectiles, the ballistic stability of the projectile on the oncoming side is better than that of the projectile on the backflow side. Whether parallel or tandem projectiles, the ballistic stability of projectile 2 becomes worse with the increase in the lateral flow velocity.

Effect of Initial Loading Position on the Propellant Particles Distribution in Two-module Charge

The propellant particles distribution in the ignition process of the modular charge has a significant effect on the interior ballistic stability. Thereinto, the particles final distribution is determined by the particles motion process. Based on the CFD-DEM method, a 3D transient gas-solid flow model is constructed to investigate the motion process and the dispersion of propellant particles. Moreover, the cold state test of the ignition process of modular charge is accomplished based on a visual ignition test platform. The simulated data are consistent with the test one. Furthermore, the effect of the initial loading position on the propellant particles distribution of two-module charge is predicted by the numerical simulation. All of two-module cases show that the distributions of particles are made up of a gentle-downhill, a horizontal, and a steep-uphill accumulation. As the initial loading position of modules moves to the right, the slope angle of the uphill is decreased first and then increased, with the minimum slope angle of 20.5°. When the initial loading position of modules is 40mm, the spatial distribution gradient of particles gets the minimum in the uphill accumulation area, and the particles axial-distribution is the most uniform.

ANALYTICAL HYPOTHESIS TO SUBSTANTIATE THE FUNDAMENTAL POSSIBILITY OF REGENERATION OF NITROCELLULOSE POWDERS AFTER LONG-TERM STORAGE WITH HYDROGEN PEROXIDE

The experience of storing ammunition shows that during long-term storage, pyroxylin powders used in ammunition are capable of arbitrarily undergoing various physical and chemical transformations, which negatively affects the ballistic characteristics of ammunition. The lack of ammunition production in Ukraine has led to the fact that ammunition is currently in operation, the storage time of which reaches 30–35 years or more.
 This article analyzes publications devoted to scientific research related to the problems of ballistic stability of gunpowders.
 A number of factors affecting the physicochemical stability of powder charges during their long-term operation are given.
 Summarizing data on the change in the main ballistic characteristics of ammunition at different periods of their storage are given.
 The analysis of chemical processes occurring in nitrocellulose gunpowder during long periods of operation is carried out, and the possibility of carrying out the regeneration of NCP by treatment with hydrogen peroxide is substantiated.
 It is assumed that one of the ways to improve the ballistic and energy characteristics of long-term ammunition can be the regeneration of nitrocellulose powder charges. It is shown that at present there are no methods for the regeneration of powder charges with long service life. However, there are encouraging data on the treatment of powders with hydrogen peroxide, on the basis of which a technology for the complete or partial restoration of the ballistic and energy characteristics of a powder charge can be developed.
 It is shown that during the regeneration of nitrocellulose powder charges with hydrogen peroxide, the calorific value of the starting material increases. It is important to note that not all of the increase in mass after NCP treatment with hydrogen peroxide can be used to compensate for the lost calorific value, however, in this case, the treatment of NCP with hydrogen peroxide should be considered an effective method for regenerating nitrocellulose powders.

Experimental Investigation of the Supercavitation and Hydrodynamic Characteristics of High-Speed Projectiles with Hydrophobic and Hydrophilic Coatings

Supercavitation technology has important application value in military and national defence fields because of its huge potential in drag reduction, while the cavitation around underwater moving objects may be affected by the surface properties of objects. In this paper, the supercavitation characteristics and hydrodynamics of a projectile with hydrophobic and hydrophilic surface coatings were experimentally studied using a high-speed camera. The supercavitation evolution, cavitation size, velocity change, drag force coefficient, and ballistic deflection of projectiles in different water depths are compared and analyzed. The results show that the length and diameter of the supercavity increase with the decrease in water depth. At the same water depth and cavitation number, the length and diameter of the supercavitation of the projectile with hydrophobic coating were greater than those of the projectile with hydrophilic coating, and the drag force coefficient of the hydrophobic projectile was obviously smaller than that of the hydrophilic projectile. Under the working conditions of 6.67D, 16.7D, and 33.3D, the drag force coefficient of the hydrophobic projectile could be reduced by about 20–40% compared with that of the hydrophilic projectile. The maximal reduction in drag force coefficient was up to 40% at σ = 0.34 under a water depth of 33.3D. The velocity attenuation of hydrophobic projectile was about 20% slower than that of hydrophilic projectile. In addition, the ballistic stability of hydrophobic coated projectiles was better than that of hydrophilic coated projectiles in the different water depths observed in the paper.

Trajectory prediction of the tapered projectile and grooved projectile in deep penetration

With the development of high-speed penetration mechanics, some typical special-shaped kinetic energy projectiles have been proposed, such as tapered and grooved projectiles. In the present study, we investigated the ballistic stability of those typical special-shaped projectiles under oblique penetration conditions, which, to our best knowledge, were not investigated before. Firstly, the geometrical description and surface meshing method of three typical projectiles (the cylindrical, tapered, and grooved projectiles) are given in detail. Then, a trajectory model is established based on the modified free-surface effect and the weak-separation effect, and the proposed model is verified by comparing with the existing tests data. Finally, influences of structural parameters and impacting conditions of the special-shaped projectiles on trajectory stability are discussed. It suggests that, compared with the cylindrical projectile, the tapered projectile has better trajectory stability, and a reasonable taper angle can reduce the lateral displacement on the premise of ensuring the vertical displacement of the projectile; For the grooved projectile, the grooves reduce the axis resistance from the targets, but the value of the groove radius has less influence on trajectory deflection. The results of this study provide a reference for the structural design of special-shaped projectiles to enhance trajectory stability.

Research on the effect of asymmetric bubbles on the load characteristics of projectiles during an underwater salvo

This paper analyzes the effect of bubbles on the load characteristic of projectiles launched underwater with transverse-flow under different dimensionless launch time intervals. The realizable k−ε turbulence model and energy equation, as well as the volume of fluid method and overlapping grid technique, were adopted. Additionally, validations of numerical approach and grids independence validation were carried out. Evolution of bubbles at tube outlet, time-domain characteristic and frequency domain characteristic of lateral force, vertical force-torque, and motion characteristics are studied. The results show that spilled gas from the tube outlet fuses and moves in a transverse-flow direction. The pressure pulsation, which is caused by the bubble elastic effect, leads to high-frequency pulsation laws of the load characteristic. In the initial stage of the movement, the motion laws of projectiles under different launch time intervals are similar. At ΔT≤1.2, the flow interference between two projectiles is large, which seriously affects the ballistic stability and safety.

Study on the penetration of elliptical cross-section projectiles into concrete targets: theory and experiment

To better understand the penetration mechanism of the elliptical cross-section projectile (ECSP) into semi-infinite concrete target, penetration experiments using three types of ECSPs with different shape ratios (1, 1.25 and 1.61) and with striking velocities ranged from 550 m/s to 1050 m/s were conducted. Penetration depths, penetration trajectory and mass erosion rates of the projectile were obtained after the experiments. The experiment results show that the penetration performance and ballistic stability of the ECSP are equivalent to those of the circular cross-section projectile (CCSP). Based on the theory of complex variable function and conformal transformation, a semi-analytical model which can calculate the cavity boundary stress distribution of elliptical section cavity controlled by the displacement boundary condition was established and the model was validated by comparing the model degenerate solution with Kirsch problem results. Theoretical calculation results show that the radial stress of elliptical section cavity increases progressively from the minor axis to the major axis. In addition, a formula combining with the semi-analytical theoretical model and the local interaction theory was developed. The predicted penetration depths were compared with 30 groups of experiment data with different projectile parameters and striking velocities and coincide quite well with the corresponding experimental data. Finally, the influence of shape ratio and caliber-radius-head (CRH) on the penetration performance of projectile and the application prospect of ECSPs on hypersonic weapon platform were studied.

NITRO CELLULOSE POWDER CHARGES OF LONG SERVICE LIFE: PROBLEMS AND THEIR POSSIBLE SOLUTIONS

One of the components of the problem of Ukraine's national security is the loading of warehouses with a variety of ammunition with an expired guaranteed storage period.
 The experience of storing ammunition shows that during long-term storage, propylene powder used in ammunition is capable of spontaneously undergoing various physical and chemical transformations, which negatively affects the ballistic characteristics of ammunition. The lack of ammunition production in Ukraine has led to the fact that ammunition is currently in operation, the storage time of which reaches 25-30 years or more.
 This article analyzes publications devoted to scientific research related to the problems of ballistic stability of propellants.
 A number of factors are presented that affect the physicochemical stability of powder charges during their long-term operation.
 The generalizing data on changes in the main ballistic characteristics of ammunition at different periods of their storage are presented.
 It is assumed that one of the ways to improve the ballistic and energy characteristics of ammunition with long service lives can be the regeneration of nitrocellulose powder charges. It is shown that at present there are no methods for the regeneration of propellant charges of long service life. However, there are encouraging data on the treatment of propellants with hydrogen peroxide, on the basis of which a technology can be developed for the complete or partial restoration of the ballistic and energy characteristics of the propellant charge.
 It is presented that the predictive assessment of changes in the characteristics of ammunition with long service lives does not correspond to their real indicators.
 It has been determined that the problem of nitrocellulose propellants of long service life is complex and, on the basis of its solution, theoretical and methodological foundations of the regeneration of nitrocellulose propellant charges can be developed to homologate the ballistic and energy characteristics of ammunition.

Impact mechanisms of aggregate on rigid projectile normal penetration into concrete target

<p indent=0mm>Concrete failure mechanisms under projectile penetration at a mesoscale level have recently attracted researchers’ attention. Based on the three-dimensional (3D) mesoscale concrete model, the influences of aggregate strength, size, and volume fraction on deflection angle and penetration resistance of projectile were analyzed during the process of rigid projectile penetration into the concrete. Four stages of projectile deflected during the process of depth penetration were described. The measurement of the deflection angle of the projectile during the penetration process revealed the factors affecting ballistic stability. These factors were investigated quantitatively, and their critical values affecting the deflection angle of projectile were obtained. The effects of the key variables of coarse aggregate on penetration resistance were quantitatively studied. Then, the applicable conditions to satisfy the homogeneous assumption and the upper bounds of aggregate size and volume fraction were identified. The latter influenced the penetration resistance and were dependent on the aggregate configurations. Finally, the influencing mechanisms of coarse aggregate on the rigid projectile normal penetration into mesoscale concrete were described. The results reported here provide a theoretical and practical background for design optimization and safety assessment for protective engineering structures.

Assessment of Impact and Ballistic Resistance of Some Types of Organoplastics

The paper represents the results of the experimental determination of impact resistance and the principles of assessing the ballistic resistance of organoplastics. Organoplastics are presented as a composite material consisting of unsaturated polyester resin (matrix) and a reinforcing component of organic origin, mainly aramid fiber. Reinforcing components are fabrics of various weaves, canvases, and discrete fiber. The polyester resin contains an additive that provides biodegradability of the binding component. In the case of using a biodegradable reinforcing component or a mineral-based reinforcing component, the organoplastics will cause minimal damage to the environment after the exploitation period. Experimental data on the impact resistance of the material were obtained on a 3 m high impact coper on the basis of fixing the work of destruction of samples of organoplastics of a certain thickness. The essence of the ballistic stability assessment was to compile a system of differential equations describing the degree of change in kinetic energy when a bullet (fragment) hits the material and the nature of the decrease in the speed of their contact in the barrier. To solve the system of equations, initial data are required: time, bullet velocity, length of the non-working part of the bullet, cross-sectional area, and mass of the bullet (fragment). The solution of the problem determines the degree of decrease in the speed of the bullet (fragment) contact with the barrier. The obtained research results are suitable for protecting the object from the impact and designing light armor protection of vehicles and other means.

IMPACT RESISTANCE OF CERAMICS IN A NUMERICAL EXPERIMENT

A series of computations based on experimental data on the depth of projectile penetration into targets is performed for verification of parameters of ballistic stability of plates made of Al2O3, B4C, and SiC ceramics. Interaction of a projectile with a steel core and a target made of an aluminum alloy with a variable-thickness ceramic plate positioned ahead of the target is simulated. The computed results are compared with experimental data for various ceramic targets 1–5 mm thick and projectile velocities of 810–850 m/s.

Firing range optimization of a 155mm uni-modular charge howitzer by ETC technology

Electrothermal-chemical (ETC) launch technology can accurately control and enhance the ignition and combustion of solid propellants to improve the consistency and accuracy of ballistics. In this paper, a calculation model including the transient burning rate formula and six-degree-of-freedom rigid body trajectory equation is established to simulate both interior and exterior ballistics processes for a 155mm uni-modular charge howitzer. The simulation results show that the muzzle velocities are optimized via the ETC technology. The 155mm uni-modular charge ETC howitzer can effectively obtain the minimum range, increase the range overlap and maximum range, and improve the ballistic stability and consistency.

Research on a Differential Geometric Guidance Law Based on Fractional-Order Theory

In this paper, fractional-order calculus theory is used to investigate the geometric law for intercepting an agile target. In order to overcome the challenges presented by the divergence of line of sight rate (LOSR) of proportional navigation (PN), the fractional LOSR is used as a compensated term in the proposed fractional differential geometric guidance law (FDGGL). By adjusting the navigation gain of the FDGGL, the new proposed guidance law can be transformed into the traditional differential geometric guidance law (DGGL) and PN. The average overload and ballistic stability of the FDGGL are analyzed based on the fractional and control theory. Some analytical results about energy consumption and trajectory variation of the FDGGL were obtained. The simulation results shows that, compared with PN and DGGL, the FDGGL has better guidance performance when intercepting different maneuvering targets.

Experimental and theoretical researches of high-speed interaction of thin obstacles with a metal fragment

The development of lightweight protective structures of increased ballistic resistance is not an easy task, since often there are conflicting requirements in terms of cost, weight, thickness, materials availability, processability, etc. To assess the effectiveness of protective structures one should use methods that allow to research the obstacles destruction when collided with high-speed particles. The paper is devoted to the actual problem of studying the ballistic stability of thin barriers made of various protective materials (steel, titanium alloy, ceramics, metal ceramics) when interacting with a metal fragment simulator a spherical steel drummer in the range of interaction speeds of about 2500 m/s. An experimental technique has been developed to study the most important indicators: the depth of a crater in an obstacle, a fragment’s velocity drop when interacting with protection, the obstacle’s and splinter’s fragments scattering in overgraded space. Mathematical modeling was carried out within the framework of continuum mechanics, which adequately describes the interaction process of the drummer and the obstacle under various impact conditions.

Effect of the Structure of Lithium-Silicate Glasses on the Mechanical Properties of Transparent Glass-Ceramic Materials

The development prospects of high-strength transparent glass-crystalline materials on the basis of lithium disilicate for protection of optical systems are found to be closely related to their structural features. We formulate the main criteria for the synthesis of transparent pyroceramics, develop model glasses of the R2O–RO–RO2–R2O3–P2O5–SiO2 system with the ratio SiO2/Li2O = 4.0 and produce glass-crystalline materials on their basis under conditions of two-stage low-temperature short-term heat treatment under production conditions. The mechanism of formation of the structure and phase composition of glass-crystalline materials on the basis of model glasses under thermal processing is investigated. The essence of the mechanism consists in the formation of lithium metasilicate nuclei-forming agents in the form of spherulites whose growth is limited by the glass phase distribution, the subsequent growth of needle-like crystals of lithium metasilicates, and their recrystallization into lithium disilicate crystals with a pronounced pseudocubic habitus pattern in the form of crossed needles and proportion of 50 vol.%, which form a layered structure in the form of dendritic needles. It is shown that a certain crystallographic orientation of lithium disilicate crystals ensures the scatter reduction of the material elastic characteristics and provides the elastic modulus as high as 307 GPa, the compressive strength of 650 MPa, and impact strength as high as 5.5 kJ/m2. It was established that the formation of a closed-form mesh block structure on the basis of 0.4 μm lithium disilicate lamellar crystals provides high-strength properties of the developed material, with a transparency in the visible part of the light spectrum, which makes it possible to use this material as the basis for obtaining transparent bullet-proof pyroceramic for the protection of optical devices of military equipment. Investigation of the ballistic stability of the developed pyroceramic and comparison of its physical and chemical properties with other known transparent ceramic high-strength materials proves the expediency of creating high-strength glass-crystalline materials on the basis of lithium disilicate to obtain transparent high-strength components for the purpose of the local protection against high-speed impact action.

Combustion Characteristics Experimental Study of Solid Hydrocarbon Propellant for Air-Turbo Rocket

The combustion characteristics of propellants heavily affect the performance of solid-propellant air-turbo rockets (SP-ATRs). In this study, an SP-ATR experimental combustion system was developed, and experimental studies were conducted on the primary and secondary combustion characteristics of two solid hydrocarbon fuel propellants. The results show that the solid hydrocarbon fuel-rich propellant, which is an ideal propellant for SP-ATRs, can play the dual role of driving the turbines and executing secondary combustion. The studies on the two candidate propellants show that CH01 has higher energy characteristics, and CH02 exhibits better performance in terms of the interior ballistic stability and ejection efficiency. For cold inflow conditions, when the fuel gas flow rate is at the optimum equivalence ratio, there are difficulties in secondary combustion. A combustion experiment with a variable gas flow rate was designed, and the upper limit of the excess air coefficient was obtained under the condition of cold inflow.