The majority of the projectiles used in the hypersonic penetration study are solid flat-nosed cylindrical projectiles with a diameter of less than 20 mm.This study aims to fill the gap in the experimental and analytic...The majority of the projectiles used in the hypersonic penetration study are solid flat-nosed cylindrical projectiles with a diameter of less than 20 mm.This study aims to fill the gap in the experimental and analytical study of the evolution of the nose shape of larger hollow projectiles under hypersonic penetration.In the hypersonic penetration test,eight ogive-nose AerMet100 steel projectiles with a diameter of 40 mm were launched to hit concrete targets with impact velocities that ranged from 1351 to 1877 m/s.Severe erosion of the projectiles was observed during high-speed penetration of heterogeneous targets,and apparent localized mushrooming occurred in the front nose of recovered projectiles.By examining the damage to projectiles,a linear relationship was found between the relative length reduction rate and the initial kinetic energy of projectiles in different penetration tests.Furthermore,microscopic analysis revealed the forming mechanism of the localized mushrooming phenomenon for eroding penetration,i.e.,material spall erosion abrasion mechanism,material flow and redistribution abrasion mechanism and localized radial upsetting deformation mechanism.Finally,a model of highspeed penetration that included erosion was established on the basis of a model of the evolution of the projectile nose that considers radial upsetting;the model was validated by test data from the literature and the present study.Depending upon the impact velocity,v0,the projectile nose may behave as undistorted,radially distorted or hemispherical.Due to the effects of abrasion of the projectile and enhancement of radial upsetting on the duration and amplitude of the secondary rising segment in the pulse shape of projectile deceleration,the predicted DOP had an upper limit.展开更多
速度目标值是市域快线的重要技术指标,它直接影响土建工程规模及设备系统的选择。以兰州轨道交通4号线为例研究分析如何选择速度目标值,根据现状公路旅行时间以及轨道交通线网对该线功能定位的要求,提出该线的时间目标值。对100、120、1...速度目标值是市域快线的重要技术指标,它直接影响土建工程规模及设备系统的选择。以兰州轨道交通4号线为例研究分析如何选择速度目标值,根据现状公路旅行时间以及轨道交通线网对该线功能定位的要求,提出该线的时间目标值。对100、120、140 km/h 3种速度目标值方案从运行时间、站间距离、旅行速度、运行能耗、系统设备、环境影响和工程投资等方面进行综合分析,最终推荐运营费用和投资较节省的100 km/h速度目标值方案。展开更多
The performance of the three-dimensional differential geometric guidance law with proportional navigation formation against a target maneuvering arbitrarily with time-varying normal acceleration is thoroughly analyzed...The performance of the three-dimensional differential geometric guidance law with proportional navigation formation against a target maneuvering arbitrarily with time-varying normal acceleration is thoroughly analyzed using the Lyapunov-like approach.The validation of this guidance law is firstly proved,and then the performance issues such as capturability,heading error control efficiency,line of sight rate convergence,and commanded acceleration requirement are analyzed,under the condition that the missile is initially flying toward the target with a speed advantage.It is proved that an intercept can occur and the line of sight rate and missile commanded acceleration can be limited in certain ranges,if the initial heading error is small and the navigation gain is sufficiently large.The nonlinear relative dynamics between the missile and the target is taken into full account,and the analysis process is simple and intuitive,due to the use of a convenient line of sight rotating coordinate system.Finally,the new theoretical findings are validated by numerical simulations.展开更多
基金the National Natural Science Foundation of China(Grant No.12102050)the Open Fund of State Key Laboratory of Explosion Science and Technology(Grant No.SKLEST-ZZ-21-18).
文摘The majority of the projectiles used in the hypersonic penetration study are solid flat-nosed cylindrical projectiles with a diameter of less than 20 mm.This study aims to fill the gap in the experimental and analytical study of the evolution of the nose shape of larger hollow projectiles under hypersonic penetration.In the hypersonic penetration test,eight ogive-nose AerMet100 steel projectiles with a diameter of 40 mm were launched to hit concrete targets with impact velocities that ranged from 1351 to 1877 m/s.Severe erosion of the projectiles was observed during high-speed penetration of heterogeneous targets,and apparent localized mushrooming occurred in the front nose of recovered projectiles.By examining the damage to projectiles,a linear relationship was found between the relative length reduction rate and the initial kinetic energy of projectiles in different penetration tests.Furthermore,microscopic analysis revealed the forming mechanism of the localized mushrooming phenomenon for eroding penetration,i.e.,material spall erosion abrasion mechanism,material flow and redistribution abrasion mechanism and localized radial upsetting deformation mechanism.Finally,a model of highspeed penetration that included erosion was established on the basis of a model of the evolution of the projectile nose that considers radial upsetting;the model was validated by test data from the literature and the present study.Depending upon the impact velocity,v0,the projectile nose may behave as undistorted,radially distorted or hemispherical.Due to the effects of abrasion of the projectile and enhancement of radial upsetting on the duration and amplitude of the secondary rising segment in the pulse shape of projectile deceleration,the predicted DOP had an upper limit.
文摘速度目标值是市域快线的重要技术指标,它直接影响土建工程规模及设备系统的选择。以兰州轨道交通4号线为例研究分析如何选择速度目标值,根据现状公路旅行时间以及轨道交通线网对该线功能定位的要求,提出该线的时间目标值。对100、120、140 km/h 3种速度目标值方案从运行时间、站间距离、旅行速度、运行能耗、系统设备、环境影响和工程投资等方面进行综合分析,最终推荐运营费用和投资较节省的100 km/h速度目标值方案。
基金This work was co-supported by the National Natural Science Foundation of China(Grant Nos.61690210 and 61690213)the National Basic Research Program of China(“973”Program,Grant No.2013CB733100).
文摘The performance of the three-dimensional differential geometric guidance law with proportional navigation formation against a target maneuvering arbitrarily with time-varying normal acceleration is thoroughly analyzed using the Lyapunov-like approach.The validation of this guidance law is firstly proved,and then the performance issues such as capturability,heading error control efficiency,line of sight rate convergence,and commanded acceleration requirement are analyzed,under the condition that the missile is initially flying toward the target with a speed advantage.It is proved that an intercept can occur and the line of sight rate and missile commanded acceleration can be limited in certain ranges,if the initial heading error is small and the navigation gain is sufficiently large.The nonlinear relative dynamics between the missile and the target is taken into full account,and the analysis process is simple and intuitive,due to the use of a convenient line of sight rotating coordinate system.Finally,the new theoretical findings are validated by numerical simulations.
