Research On The Characteristics Of Penetration Trajectory Of Elliptical Cross-section Projectile Into Metal Targets

With the development of modern defense technology,important military targets have been underground and fortified,which puts forward higher requirements for the improvement of the penetration ability of the projectile.At the same time,the rapid development of hypersonic vehicle platforms has also brought new challenges to the design of kinetic energy projectiles.The traditional circular section warhead is difficult to meet the needs of the heterogeneous payload space of the hypersonic weapon platform,so it is urgent to develop the special-shaped section warhead represented by the elliptical cross-section and its related technologies.The elliptical cross-section warhead has the advantages of good adaptability of the weapon platform and high utilization rate of the payload space,so it has become the most suitable preferred option for hypersonic weapon platforms.The elliptical cross-section warhead exhibits significant asymmetric characteristics due to its special structure,which are different from that of the traditional circular section warhead.And that has a significant influence on the penetration process of elliptical cross-section warhead into typical targets,especial for the penetration trajectory.Thus,it is imminent to study the penetration trajectory characteristics of elliptical cross-section warheads penetrating typical targets.In this paper,the combination of theoretical analysis and experimental research is used to study the characteristics of penetration trajectory of elliptical cross-section warheads(hereinafter referred to as the projectiles)into metal targets.The main work and results are as follows:(1)Study on the characteristics of two-dimensional penetration trajectory of projectile into thick metal targetsThe penetration experiments of projectile with striking velocities ranging from 700m/s to1100m/s and oblique angle of 0°,10°,20°,40° were conducted based on the 14.5mm ballistic gun,which the length to diameter(L/D)of the projectiles were 3 and 4,respectively.And the failure modes of target and penetration trajectory were obtained.Next,the two-dimensional penetration trajectory model of projectile penetration into thick metal targets was developed based on the local interaction theory and dynamic expansion theory,where the effects of free surface and wake separation/reattachment between projectile and target were taken into account.Then,the influence of the effects of free surface and wake separation/reattachment between projectile and target on penetration trajectory were analyzed by combining with experimental data and calculated results.In addition,the influences of oblique angle,striking velocity,and L/D of projectile on the penetration trajectory were discussed.Among them,the oblique angle had the most significant effect on the penetration trajectory.(2)Study on the characteristics of three-dimensional penetration trajectory of elliptical cross-section projectile into thick metal targetsA three-dimensional penetration trajectory model of elliptical cross-section projectile was established based on the two-dimensional penetration trajectory model of circular section projectile,where the major axis to minor axis ratio of the cross-section,the angle around the projectile axis,the pitch,yaw,oblique angle and angular velocity to the plane of obliquity on the penetration trajectory were further considered.Next,the oblique penetration experiment of the elliptical cross-section projectile with two aspect ratios to 2A12 aluminum alloy thick targets was carried out,and the experimental data of penetration trajectory was obtained.The three-dimensional penetration trajectory model was validated by the experimental data.Finally,the influence of the ratio of major axis to minor axis of elliptical cross-section projectile,and the angle around the axis of the elliptical cross-section projectile on the penetration trajectory of elliptical cross-section projectile and the pitch,yaw,coupled pitch and yaw,and angular velocity vertical to the plane of obliquity on the penetration trajectory of the circular section projectile were analyzed.The results showed that the angle around the projectile axis,the pitch,the coupled pitch and yaw were the main factors leading to the transformation of the penetration trajectory from two-dimensional to three-dimensional.(3)Study on the normal perforation of elliptical cross-section projectile into finite-thick metal targetsThe elastic decay-plastic decay-cracking three-stage penetration model was employed to develop the normal perforation model of a projectile into a finite-thick metal target based on the spherical dynamic cavity expansion theory.Subsequently,the experiment of two kinds of crosssection projectiles perforating the 30 mm thick 2A12 aluminum alloy targets was carried out,and the penetration characteristics of the elliptical cross-section projectile and circular section projectile were obtained.Furthermore,the perforation model was validated by existing and experimental data in this paper.Finally,the relationship between the striking factor of elliptical cross-section projectile and the non-dimensinal target thickness was analyzed.The critical nondimensional target thickness under different striking factor of elliptical cross-section projectile was obtained theoretically,which was used to judge whether the target was finite thickness.Besides,the influence of the non-dimensional head shape factor of the elliptical cross-section projectile on the process of penetration was further analyzed.(4)Research on the characteristics of penetration trajectory of elliptical cross-section projectile to single layer metal targetThe penetration trajectory model of the elliptical cross-section projectile to single layer metal target was established based on the normal perforation model of elliptical cross-section projectile into finit-thick metal targets,where the initial penetration conditions of the projectile and the influence of the front free surface of the target on the penetration process were further considered.Next,the experiments of two kinds of cross-section projectile oblique penetration into single-layer 2A12 aluminum alloy and 921 A armored steel target were carried out,and the experimental data of elliptical cross-section projectile and circular cross projectile was obtained.Then,the penetration trajectory model was validated by combining the existing and the experimental data in this paper.Finally,the influence of the oblique angle,the target thickness and the striking velocity of elliptical cross-section projectile on the penetration trajectory were analyzed,respectively.The results showed that the stability of elliptical cross-section projectile is equivalent to that of the circular cross projectile regardless of the influence of the angle around the projectile axis.(5)Research on the characteristics of penetration trajectory of elliptical cross-section projectile into space layered metal targetsThe penetration trajectory model of elliptical cross-section projectile penetrating space layerd targets obliquely was developed based on the penetration trajecoty model of elliptical cross-section projectile penetrating a single-layer metal target obliquely,which the influence of shank of projectile and spacing interval between targets were taken into consideration comprehensively.Then,the experiments of circular section projectile oblique penetration into space layered targets were carried out and the model was verified by combining the experimental data.Finally,the effects of oblique angle,impact velocity and spacing interval between targets on penetration trajectory of elliptical cross-section projectile were analyzed respectively.The results showed that the penetration trajectory was controlled by the coupling of the oblique angle,the striking velocity of the projectile and the spacing interval between the target plates.