超高速碰撞产生等离子体及其对逻辑芯片的干扰效应

为理解和评估超高速碰撞产生等离子体及其对航天器逻辑芯片的电磁干扰效应,进行二级轻气炮强冲击加载实验模拟超高速撞击;利用郎缪尔三探针诊断系统对弹丸撞击2A12铝板产生等离子体的电子温度和电子密度在给定位置处进行诊断测量,建立逻辑芯片信号采集系统对给定位置处逻辑芯片遭受干扰进行监测分析。结果表明,撞击速度在2.5~3.5km/s范围时均能产生等离子体,等离子体电子温度和电子密度均随撞击速度而增加,其中电子密度与撞击速度呈指数关系。超高速碰撞产生等离子体对逻辑芯片运行状态的干扰主要表现为三种形式,分别是传输信号瞬态中断而后恢复、输出逻辑关系短暂失真和逻辑门失效。     

铝弹丸超高速正撞击铝合金薄板产生溅射物云特性研究

为研究微流星体或空间碎片超高速正撞击航天器表面缓冲结构产生的溅射物形态和分布特性,采用二级轻气炮驱动铝弹丸进行超高速撞击实验。铝弹丸超高速正撞击铝合金薄板首先溅射高温微粒子或甚至是微小熔滴等闪光热源,随后是由金属粉尘及低速碎片粒子构成的溅射物云团簇。正撞击产生的溅射云团簇在空间呈环锥形状分布,3~5 km/s速度范围内,撞击速度越高,分布越密集。利用HSFC-PRO超高速相机捕捉到撞击初始阶段产生的溅射物在不同时刻的影像演化,通过跟踪影像中溅射闪光热源和溅射云团簇最前端的轮廓估算其一维膨胀速度。非球弹丸撞击时的姿态偏转可能对溅射物云团簇的分布有较大影响。     

诱发供电太阳能电池阵放电的临界碰撞速度研究

为了获得高速碰撞供电太阳能电池阵产生等离子体诱发放电的临界碰撞速度,利用建立的对太阳能电池阵供电的外电路系统、放电电流和放电电压数据采集系统,结合二级轻气炮加载系统进行了弹丸入射角度均为60°、供电电压均为100 V且碰撞速度分别为2.0,2.2,2.4,2.6和2.8 km/s条件下高速碰撞铝基板太阳能电池阵放电情况的数据采集。实验结果表明,碰撞速度为2.0,2.2和2.4 km/s时未测到等离子体的特征参量、放电电压和放电电流;碰撞速度为2.6和2.8 km/s时测到了等离子体的特征参量和放电参量。由此可以断定,在给定实验条件下高速碰撞供电太阳能电池阵产生等离子体诱发放电的临界碰撞速度介于2.4~2.6 km/s间。     

常压微波等离子体激发过程的数字研究

基于常压微波等离子体产生装置的三维数字模型用于分析等离子体产生过程中电场、反射系数等物理参数的变化和等离体的特性。三维数字模型建立在包括气体放电物理过程、边界条件和工作气体碰撞反应等大量的电磁学、流体力学、化学以及分子动力学的学科理论模型基础上，对多个参数进行耦合计算。计算结果表明：等离子体的激发是一个快速、剧烈的过程，在2.5×10-7^s时，放电区域的气体电离达到最高峰，0.1 s时等离子体就已趋于稳定。同时激发气体产生等离子体所消耗的微波功率在等离子体激发过程中先急速增大，到达峰值后缓慢减小。     

圆柱形长杆超高速正碰撞薄板结构破碎效应

超高速碰撞多层板结构破碎效应研究对空间碎片防护及动能武器毁伤效应研究有着重要意义。采用ANSYS/AUTODYN程序的SPH方法,对超高速碰撞碎片云的形成过程进行了数值模拟,某典型时刻一次及二次碎片云形貌的数值模拟结果与实验结果吻合较好,验证了计算方法和模型参数的正确性。在此基础上采用数值模拟方法,对钨合金、轧制均质装甲(Rolled Homogeneous Armor,RHA)及LY12铝三种材料的圆柱形弹体超高速碰撞薄板的破碎规律进行了研究,基于量纲分析方法得出了弹体破碎长度随弹靶材料特性、弹靶尺寸及初始撞击速度变化的关系式。并研究了钨合金及RHA两种材料的长杆弹对八层RHA板结构的超高速碰撞效应。     

微小碎片超高速撞击太阳电池阵的研究进展

概述了空间环境下微小碎片超高速撞击太阳电池阵的影响,不仅对太阳电池阵造成机械损伤,还诱发持久电弧放电,对其寿命和可靠性形成威胁。详细介绍了日本、欧洲、中国等一些国家在本领域的研究状态、研究特点,对实验中涉及的对瞬态等离子体诊断和等离子体诱发二次放电进行了重点介绍。提出了加快我国空间碎片超高速撞击特性研究的建议,这也是做好卫星太阳电池阵防护的重要途径。     

用于空间辐射主动防护的等离子体发生器设计

等离子引发磁膨胀技术被美国航空航天局推荐为最有工程应用价值的空间辐射主动防护技术。在该技术中,高密度等离子体发生器的设计是其中的关键技术之一。本文设计了一种高密度螺旋波等离子体发生器,采用13.56 MHz射频源激发等离子体天线,并将该等离子发生器偏心放置在表面磁感应强度为0.1 T的柱状永久磁铁内,以氩气为工作气体进行了真空舱磁膨胀实验。利用朗缪尔探针,对发生器产生的等离子体密度及温度随输入功率的变化进行了测量,该发生器成功地引发了磁铁磁场膨胀。     

圆柱碰撞冲击噪声理论分析与数值仿真

基于接触动力学相关理论和弹性体线接触理论模型,建立了圆柱碰撞冲击理论数学模型,结合声学理论对圆柱碰撞冲击辐射噪声进行了理论预估。采用有限元法与瞬态边界元法相结合的瞬态噪声数值仿真方法,对圆柱碰撞冲击噪声进行数值仿真,实现了瞬态冲击噪声辐射声波的可视化。分析结果表明圆柱碰撞冲击噪声主要由加速度辐射噪声产生,圆柱碰撞冲击噪声辐射声场具有明显指向性。对比理论分析结果、数值仿真结果以及Hertz点接触模型计算结果可知,理论分析结果与数值仿真结果吻合较好,而Hertz点接触模型将圆柱体线接触模型简化为点接触模型,导致接触时间延长,接触力和冲击噪声幅值降低。基于数值仿真方法及理论分析,研究了冲击速度及材料弹性模量对圆柱碰撞冲击噪声的影响。     

大面积等离子体片分层现象的实验研究

为了研究大面积等离子体片的分层特性,利用脉冲磁约束线形空心阴极放电装置,在150 Pa氦气中产生了持续时间为200μs、面积为60 cm×60 cm的大面积等离子体片。采用快帧法和旋转空心阴极法利用郎缪尔探针首次获得了等离子体片分层时厚度方向电子密度分布及其演化构成的二维分布图;基于获得的二维分布图,研究了分层等离子体片厚度方向电子密度的分布特征与磁场强度和放电电流的关系。实验发现,等离子体片分层时厚度方向电子密度呈现双峰曲线分布特征;当放电电流为2 A,磁场强度为1.5×10~(-2),2.25×10~(-2),3×10~(-2)T时,双峰间距分别为0,3.2,8.4 mm;当磁场为3×10~(-2)T,电流为1,2,3,4 A时,双峰间距分别为8.6,8.2,6.8,5 mm。结果表明:分层等离子体密度峰值间距随着磁场的增强和放电电流的降低而增大。     

单壁碳纳米管中氢等离子体的微波损耗机理研究

运用双流体理论,在同时考虑了单壁碳纳米管中氢等离子体的电子碰撞吸收和氢离子碰撞吸收的基础上,理论推导出了铁催化高压歧化生成的单壁碳纳米管中氢等离子体的微波衰减系数公式,计算了0．2GHz-18GHz频段的微波衰减系数。数值结果表明,铁催化高压歧化生成的单壁碳纳米管中氢等离子体对2．45GHz的微波产生强烈损耗。理论值与实验数据相吻合。     

The production and evolution of impact-generated magnetic fields

The production of magnetic fields within impact-generated plasma may explain magnetic fields that have been observed during hypervelocity impact experiments at the NASA Ames Vertical Gun Range. The effect of impact angle on the production and subsequent evolution of impact-generated magnetic fields is assessed using magnetic field data obtained during macroscopic hypervelocity impacts conducted within two ambient magnetic field environments. The configuration and duration of spontaneous impact-generated magnetic fields are round to have a strong dependence on impact angle, exhibiting a smooth transition from a cylindrically symmetric field configuration at vertical incidence to a strong bilaterally anti-symmetric field configuration at high obliquity; hence, crater-related paleomagnetic fields may yield a diagnostic signature of impact angle where other clues (shape, ejecta pattern) are absent or ambiguous. As direct result of some surprising experimental results, a first-order model of field generation during the cavitation regime of high incidence angle hypervelocity impacts is explored. A possible consequence of this model is that magnetic fields produced during hypervelocity impacts (especially those that form large craters) may be an important component of planetary magnetism—especially lunar magnetism during the last 3.6 billion years.     

高速粒子撞击作用下LF6合金多层靶结构防护能力研究

针对总厚度为４ｍｍ的ＬＦ６合金双层靶和总厚度为２ｍｍ的三层靶进行了直径为２ｍｍ,速度分别为５．８和７．２ｋｍ／ｓ的ＧＣｒ１５粒子 撞击试验,并对双层靶进行了不同前靶厚度和靶间距的撞击试验,试验结果表明：与同样碰撞条件下半无限体靶上产生的破坏情况相比,多层靶被击穿的总厚度远淖于半无限体靶上形成的弹坑深度,采用多层靶结构可显著提高材料的抗高速粒子撞击能力,并大大降低航天器抗高速粒子撞击的防护结构的重量     

Crater distribution on the rear wall of AL-Whipple shield by hypervelocity impacts of AL-spheres

All spacecraft in low orbit are subject to hypervelocity impact by meteoroids and space debris, which can in turn lead to significant damage and catastrophic failure. In order to simulate and study the hypervelocity impact of space debris on spacecraft through hypervelocity impact on AL-Whipple shield, a two-stage light gas gun was used to launch 2017-T4 aluminum alloy sphere projectiles. The projectile diameters ranged from 2.51 mm to 5.97 mm and impact velocities ranged from 0.69 km/s to 6.98 km/s. The modes of crater distribution on the rear wall of AL-Whipple shield by hypervelocity impact of AL-spheres in different impact velocity ranges were obtained. The characteristics of the crater distribution on the rear wall were analyzed. The forecast equations for crater distribution on the rear wall of AL-Whipple shield by normal hypervelocity impact were derived. The results show that the crater distribution on the rear wall is a circular area. As projectile diameter, impact velocity and shielding spacing increased, the area of crater distribution increased. The critical fragmentation velocity of impact projectile is an important factor affecting the characteristics of the crater distributions on the rear wall.     

Hypervelocity penetration of plate targets by rod and rod-like projectiles

This paper has summarized the results of experimental tests and analytical studies of the hypervelocity impact of rod and rod-like projectiles which were conducted at the Naval Research Laboratory. The results presented here provide relatively simple analytic expressions from which one can calculate the results of a hypervelocity impact of a rod or rod-like projectile even into complex targets under most impact configurations of interest. The methodology does require a knowledge of certain empirical constants which depend on the projectile and target materials. For those cases where the values of these constants have not been provided, they can easily be determined by performing a relatively few experimental impacts.     

基于A-T模型的长杆弹超高速侵彻陶瓷靶体强度分析

Alekseevskii-Tate(A-T)模型广泛应用于长杆弹超高速冲击的终点效应分析中。A-T模型对于金属弹靶强度有明确的表达式,而对于陶瓷靶体强度尤其是弹体初始冲击速度大于1 500 m/s时还没有统一的结论。基于长杆钨弹超高速(1 500~5 000 m/s)侵彻三种陶瓷(Al N,B4C,Si C)/铝复合靶体的缩比逆弹道实验数据;基于A-T模型,给出了上述陶瓷材料在不同侵彻速度范围内的靶体强度表达式。进一步通过与47发长杆钨弹超高速(1 250~2 500 m/s)侵彻陶瓷(Al N,B4C,Si C,AD85)/RHA钢复合靶体DOP实验数据对比,验证了提出的陶瓷靶体强度表达式的适用性。     

Simulations of hypervelocity impact damage and fracture of aluminum targets using a constitutive-microdamage material model

The material damage and fracture of Aluminum 1100 target plates that experience hypervelocity impact by glass projectiles traveling at 6 km/s are simulated using a proposed constitutive-microdamage material model. The model is best suited for polycrystalline metals that are subject to hypervelocity impact at the lower range of velocities. Simulations are performed for three projectile diameter-target thickness ratios that produce a wide range of damage features. The predicted damage is compared with that of the corresponding test laboratory specimens, illustrating the capability of the constitutive-microdamage model.     

Hypervelocity impact on isotropic composites with metal or ceramic inclusions

Experimental results of studying the hypervelocity impact on isotropic heterogeneous composites consisting of an epoxy or aluminum matrix containing fine-grained metal (Al, Pb) or ceramic (SiO₂) inclusions are given. The aim of the study is to develop composite materials offering higher penetration resistance to a high-velocity projectile than the component material. This resistance is characterized by the magnitude of the ratio of the crater depth in a thick target to the diameter of spherical projectile. In the case of two particulate composites studied it is shown that the crater depth from impact of steel projectiles is lower about by one projectile diameter than for homogeneous lead or aluminum over the impact velocity ranged from 3 up to 11 km/s.     

Hypervelocity penetration modeling: momentum vs. energy and energy transfer mechanisms

Analytic penetration modeling usually relies on either a momentum balance or an energy-rate balance to predict depth of penetration by a penetrator based on initial geometry and impact velocity. In recent years, fairly sophisticated models of penetration have arisen that develop the three-dimensional flow field within a target. Based on the flow field and constitutive assumptions, it is then possible to derive a momentum or an energy-rate balance. This paper examines the use of assumed flow fields within a target created by impact and then examines the resulting predicted behavior based on either momentum conservation or energy conservation. It is shown that for the energy-rate balance to work, the details of the energy transfer mechanisms must be included in the model. In particular, how the projectile energy is initially transferred into target kinetic energy and elastic compression energy must be included. As impact velocity increases, more and more energy during the penetration event is temporarily deposited within the target as elastic compression and target kinetic energy. This energy will be dissipated by the target at a later time, but at the time of penetration it is this transfer of energy that defines the forces acting on the projectile. Thus, for an energy rate balance approach to successfully model penetration, it must include the transfer of energy into kinetic energy within the target and the storage of energy by elastic compression. Understanding the role of energy dissipation in the target clarifies the various terms in analytic models and identifies their origin in terms of the fundamental physics. Understanding the modes of energy transfer also assists in understanding the hypervelocity result that penetration depth only slowly increases with increasing velocity even though the kinetic energy increases as the square of the velocity.     

Experimental measurements of hypervelocity impact plasma yield and energetics

Ion yields and their characteristic energies have been measured experimentally in the plasma produced by hypervelocity impacts of iron rrmicroparticles on rhodium in the range 1.2 to 87 km s'. The ion yield shows a greater velocity dependence than has generally been reported in the literature, though the difference is attributed to experimental and analytical effects. The higher value derived here is believed to be a better representation for the yield of plasma from the primary impact. The impact plasma is shown not to be in thermal equilibrium. Characteristic energies of the target and projectile material ions typically lie in the range 20-40 eV (also higher than values generally quoted in the literature) and show little variation with impact velocity, while contaminant ions (alkali metals and hydrogen) show significantly different trends indicating a different production mechanism.     

椭球弹丸超高速撞击防护屏碎片云数值模拟

低地球轨道的各类航天器易受到微流星体及空间碎片的超高速撞击.本文采用AUTODYN软件进行了椭球弹丸超高速正撞击及斜撞击防护屏碎片云的数值模拟.给出了三维模拟的结果.研究了在相同质量的条件下,不同长径比椭球弹丸以不同速度和入射角撞击防护屏所产生碎片云的特性,并与球形弹丸撞击所应产生的碎片云特性进行了比较.结果表明:在相同的速度下,不同长径比椭球弹丸撞击的碎片云形状、质量分布和破碎程度是不同的,随撞击入射角的增加弹丸的破碎程度增大,滑弹碎片云的数量增加;随撞击速度的增加,弹丸的破碎程度也增加.