力学进展  2019 , 49 (1): 201904-201904 https://doi.org/10.6052/1000-0992-17-021

长杆高速侵彻问题研究进展

焦文俊12, 陈小伟34

1 中国科学技术大学近代力学系, 合肥 230027
2 中国工程物理研究院总体工程研究所, 四川绵阳 621999
3 北京理工大学爆炸科学与技术国家重点实验室, 北京 100081
4 北京理工大学前沿交叉科学研究院, 北京 100081

Review on long-rod penetration at hypervelocity

JIAO Wenjun12, CHEN Xiaowei34

1 Department of Modern Mechanics, Universityof Science and Technology of China, Hefei 230027, China
2 Institute of Systems Engineering, China Academy of Engineering Physics, Sichuan, Mianyang 621999, China
3 The State Key Lab of Explosion Science and Technology,Beijing Institute of Technology, Beijing 100081, China
4 Advanced Research Institute for Multidisciplinary Science,Beijing Institute of Technology, Beijing 100081, China

中图分类号:  O385

文献标识码:  A

通讯作者:  †E-mail: chenxiaoweintu@bit.edu.cn

收稿日期: 2017-11-25

接受日期:  2018-04-9

网络出版日期:  2019-01-15

版权声明:  2019 开云棋牌官方  This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

基金资助:  国家杰出青年基金(11225213)和国家自然科学基金(11872118)资助项目

作者简介:

陈小伟, 教授, 博导.2017年1月入职北京理工大学前沿交叉科学研究院.国家杰出青年科学基金获得者(2012), 国家首批中青年科技创新领军人才(2013), “万人计划”首批科技创新领军人才(2014). 北京大学理学学士(1989), 香港科技大学理学硕士(1999), 新加坡南洋理工大学工学博士(2003). 曾获中国工程物理研究院首批杰出专家(2012),中物院第12届邓稼先青年科技奖(2010)和第8届于敏数理科学奖(2010),中国科协“求是”杰出青年实用工程奖(2012), 四川省学术技术带头人(2014).1989.12—2017.01在中物院总体工程研究所工作,长期从事复杂结构力学、结构冲击动力学、穿甲动力学和常规武器战斗部设计的研究,在穿甲/侵彻力学领域已开展有国际影响的独创性系统研究,工作涵盖深侵彻、金属靶穿甲、弹体响应与失效破坏和战斗部结构分析等,其成果已在国内外同领域产生了较大影响. 已取得9项部委级科技进步奖(其中二等奖5项), 发表论文130余篇 (其中SCI收录近60篇),国内外大会报告和院校邀请报告60余次.担任工程材料与结构冲击与振动四川省重点实验室主任, 担任International Journal of ProtectiveStructures,《爆炸与冲击》《振动与冲击》《兵工学报》《应用数学和力学》《含能材料》《防护工程》《解放军理工大学学报(自然科学版)》编委, 担任西南科技大学讲座教授,中物院研究生院、北京大学工学院、解放军陆军工程大学冲击爆炸防灾减灾国家重点实验室、北京理工大学安全与防护协同创新中心和中国科技大学兼职教授/兼职博导.

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摘要

由高密度金属制成的长杆弹在1.5$\sim$3.0km/s的下具有很强的侵彻和贯穿能力,长杆高速侵彻问题现已成为穿甲侵彻领域的研究热点.本文综述了长杆高速侵彻问题的最新研究进展,首先介绍了长杆高速侵彻的基本概念、研究方法和理论模型;其次重点论述了研究中关注的突出问题与应用, 包括弹靶材料性质、长杆弹头部形状、长径比效应与分段杆设计、陶瓷靶抵抗长杆侵彻与界面击溃和非理想长杆侵彻;最后对未来的研究工作提出一些建议.

关键词: 长杆弹 ; 高速 ; 侵彻 ; 理论模型 ; 穿甲力学

Abstract

Made by high-density metals, long-rod penetrators have excellent performances on penetration and perforation when launched at hypervelocities around 1.5$\sim $3.0km/s. Due to their important background in the military application, long-rod penetration at hypervelocity has become an active research focus. The present paper reviews research advance up-to-date on long-rod penetration at hypervelocity. Firstly, basic concepts, research methods, and theoretical models are introduced. Secondly, highlighted issues which are focused in past studies and their applications, including rod and target materials, nose shape, $L/D$ effect and segmented rods, ceramic targets and interface defeat, as well as non-ideal long-rod penetration, etc. Finally, some future research proposals are suggested.

Keywords: long-rod penetrator ; hypervelocity ; penetration ; theoretical models ; penetration mechanics

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焦文俊, 陈小伟. 长杆高速侵彻问题研究进展[J]. 力学进展, 2019, 49(1): 201904-201904 https://doi.org/10.6052/1000-0992-17-021

JIAO Wenjun, CHEN Xiaowei. Review on long-rod penetration at hypervelocity[J]. Advances in Mechanics, 2019, 49(1): 201904-201904 https://doi.org/10.6052/1000-0992-17-021

1 引 言

侵彻与穿甲问题的研究具有悠久的历史, 到目前为止,刚性弹的侵彻与穿甲问题已取得诸多研究成果, 形成了较为完善的理论体系(Goldsmith 1999, 陈小伟 2009, 钱伟长 1984).基于刚性杆在一定的速度范围内的无量纲侵彻深度正比于其动能的认识,产生了直接利用动能杀伤目标的动能武器 (kinetic energy weapon).

动能武器的核心是由钨合金和贫铀合金等高密度金属制成的长杆弹芯.长杆弹长径比 $(L / D)$大、密度高、飞行速度快 (数倍于兵器速度),单位截面积上具有很高的动能, 因而具有很强的侵彻与贯穿能力.自20世纪60年代起,高密度金属制成的长杆弹就取代了比其短得多的钢弹成为了坦克弹药.相传美军计划在2025年前部署的新型概念武器“上帝之杖”,其核心就是从太空中发射由钨、钛或铀金属制成的长杆.

长杆高速侵彻与刚性弹侵彻最大的区别在于, 当弹体高速作用于靶体上时,作用面上压力远高于材料强度, 弹靶发生严重质量侵蚀,其变形模式为半流体, 即在弹靶界面处接近流体而在远处仍可视作刚体(如图1所示). 因此,本文中的“高速”区别于刚性弹侵彻的“低速”和流体侵彻的“超高速”,特指使弹靶发生半流体变形的撞击速度.不同速度下长杆弹侵彻机理的变化将于后文详述. 此外还需说明的是,本文论述中大部分靶体为半无限厚靶, 涉及少量中厚靶,不涉及薄靶——薄靶撞击问题在机理

图1   长杆侵彻中弹靶变形模式示意图$(v$为弹尾(刚体)速度即撞击速度,$u$为弹头 (流体)速度即侵彻速度) (Walker & Anderson 1995)

   

上有很大差异, 对此Hermann和Wilbeck(1987)以及Piekutowski(1996)都有较好的综述可以参阅.

受限于发射技术, 长杆高速侵彻问题的研究始于20世纪五六十年代.Allen和Rogers(1961)最早公开发表对长杆高速侵彻问题的研究,他们运用二级轻气炮和逆向弹道技术开展了7075-T6铝圆柱撞向不同材料制成的固定长杆的实验,并在理论分析中采用了与Eichelberger(1956)分析聚能射流类似的方法,形成了长杆侵彻最早的理论分析模型. Eichelberger和Gehring(1962)以及Christman和Gehring(1966)基于实验观测提出了长杆高速侵彻的4个典型阶段,对侵彻机理的认识具有重要意义. Alekseevskii(1966)和Tate(1967,1969)几乎同时且独立地给出了更完备的长杆半流体侵彻的理论分析模型.在随后的半个多世纪内, Alekseevskii-Tate模型被无数次地讨论和应用,成为分析长杆高速侵彻问题首选的理论模型.

自20世纪七八十年代起, 长杆高速侵彻领域开展了大量实验.西德恩斯特马赫研究所 (Ernst Mach Institute, EMI)的Hohler和Stilp(1977)开展的$L / D =10$钨合金长杆弹侵彻半无限厚装甲钢靶的实验成为后来检验理论模型和数值模拟的标准.Silsby(1984)进行了更大长径比 $(L/ D = 32)$和更大尺寸的实验.Hohler和Stilp(1987)总结了已发表的实验数据,讨论了侵彻深度、弹坑半径等与撞击速度、弹靶材料以及长径比的关系.其中提出的长径比效应后来成为长杆侵彻一个相当重要的特征效应.美国陆军弹道研究实验室 (Ballistic Research Laboratory,BRL)的Sorensen等(1991)总结了钨合金连续和分段长杆侵彻轧制均质钢(Rolled Homogeneous Armor, RHA)的全尺寸与半尺寸实验.美国西南研究院 (Southwest Research Institute, SwRI)的Anderson等(1992a)编辑了侵彻数据库,对此前开展的终点弹道实验数据进行了较全面的搜集整理.

进入20世纪90年代, 闪光X射线 (flash X-ray,FXR)摄影技术被应用于高速侵彻试验诊断中 (Hohler et al. 1995,Subramanian et al. 1995),其可记录弹靶变形的中间形态、弹靶界面移动和长杆弹侵蚀的时程关系,为理论分析提供了更详细的信息. 其中, Orphal等 (Behner et al. 2006;Orphal 1997; Orphal & Franzen 1990, 1997; Orphal & Miller 1991; Orphal et al. 1996,1997)对分段杆和陶瓷靶抵抗长杆侵彻的实验较有代表性.早期实验研究主要是通过对大量实验数据的总结,归纳出在一定范围内适用的经验公式, 最直接但效率偏低;近期实验注重对侵彻过程中新物理现象的观测,需进一步结合数值模拟和理论分析深入研究侵彻机理变化.

二维计算程序诞生于20世纪60年代, 并于七八十年代发展成熟 (Anderson 1987). 美国桑迪亚国家实验室 (Sandia National Laboratories,SNL)的二维欧拉流体动力学程序CSQ是最早用来模拟长杆侵彻问题的工具,也是三维流体动力学程序CTH的前身(McGlaun 1990). Anderson等 (Anderson & Orphal 2003,2008; Anderson & Walker 1991; Anderson et al. 1993, 1995,1996, 1999b)利用CTH对长杆侵彻作了一系列的模拟,其中Anderson和Walker(1991)对$L /D=10$钨合金长杆以1.5km/s侵彻RHA的模拟得到了比Alekseevskii-Tate模型更贴近实验的结果,他们分析了产生差异的原因,并在此基础上提出了一个与时间相关的理论模型 (Walker & Anderson 1995). 以色列防务技术研究院RAFAEL公司的Rosenberg等(Rosenberg & Dekel 1994a, 1996, 1998, 1999, 2000, 2003;Rosenberg et al. 1995, 1997a, 1998)运用2D欧拉程序PISCES2DELK进行了一系列数值模拟,分析了弹头形状、长径比、弹靶强度以及其他材料参数等因素对长杆侵彻的影响.通过数值模拟, 侵彻过程中的压力、速度和几何等细节信息得以获得.然而, 数值模拟结果与计算方法和材料本构的选取密切相关,且相关参数的选取也具有较强的人为性,故其准确性往往需要与实验和理论对比来验证.

国际上在长杆高速侵彻领域比较活跃的有Hohler和Stilp, Anderson,Orphal以及Rosenberg等研究组, 其所著的综述 (Anderson 2003, 2017;Orphal 2006; Stilp & Hohler 1995)和专著 (Rosenberg & Dekel 2012)侧重于介绍各自在该领域的工作进展.国内学者对长杆高速侵彻问题的研究起步较晚,但对于一些特定材料与特殊问题的研究已取得一些有意义的成果.陈小伟和陈裕泽对长杆高速侵彻陶瓷靶问题撰写了代表性综述 (陈小伟等 2006), 同时陈小伟教授课题组还在长杆高速侵彻理论 (Jiao & Chen 2018)、界面击溃效应 (Li & Chen 2017; Li et al. 2014,2015b; 李继承等 2011a, 2011b)、纤维增强金属玻璃长杆弹 (Chen et al.2015, Li et al. 2015a,李继承等 2011c, 陈小伟等 2012, 王杰等 2014)、分段杆 (郎林等 2011)和可压缩性 (Song et al. 2017a, 2017b,2018)等方面开展了一系列研究.中国科学技术大学文鹤鸣教授课题组开展了长杆侵彻的一维理论和模拟研究(He & Wen 2013; Lan & Wen 2010; Lu & Wen 2018; Wen & Lan 2010; Wen et al. 2010, 2011; Zhou & Wen 2003; 兰彬等 2008, 2009),北京理工大学黄风雷教授团队对长杆侵彻陶瓷靶、金属靶和混凝土靶开展了实验、模拟和理论研究(Zhang & Huang 2004, 张连生等 2005, 李志康和黄风雷 2010,李金柱等 2014, Li et al. 2017),南京理工大学张先锋教授课题组研究了长杆高速撞击陶瓷靶和界面击溃效应(Zhang & Li 2010; Zhang et al. 2011; 谈梦婷等 2016, 2017,2018),解放军理工大学方秦教授课题组开展了长杆高速侵彻的实验和理论分析(Kong et al. 2016b; Kong et al. 2017b, 2017c; 孔祥振等 2017;翟阳修等 2017).

本文将对长杆高速侵彻问题的研究进展展开全面综述. 文章主体分为两部分:第一部分介绍长杆高速侵彻的基本概念、研究方法和理论模型;第二部分结合军事应用背景重点给出研究中关注的突出问题与应用.最后对未来研究工作提出一些建议.

2 长杆高速侵彻的基本概念

本节所述的基本概念在长杆侵彻研究中比较重要, 后文论述中将大量涉及,故有必要在此重点论述.

2.1 长杆弹的不同侵彻模式

长杆侵彻问题研究的核心是通过建立侵彻速度$u$与撞击速度$v$的关系来描述弹靶相互作用,而$u$--$v$关系的建立与侵彻模式直接相关. 一般说来,根据弹体强度和靶体阻力的相互关系,长杆侵彻问题可以分为弹体强度高于靶体阻力和弹体强度低于靶体阻力两类情况分别分析.

长杆高速侵彻 (半流体侵彻)的速度范围大致为1.5--3.0km/s,不同弹靶材料对应的侵彻速度范围存在差异.在超过3.0km/s的超高速碰撞下, 将发生完全的流体侵彻,弹靶强度影响可以忽略, 同时需要考虑冲击波和可压缩性等因素.在低于1.5km/s的低速撞击下, 长杆将以刚性弹的方式侵彻或无法侵彻(形成界面击溃). 在临界速度范围内, 对应不同的弹靶强度关系,将发生两类典型的侵彻模式转变.

2.1.1 弹体强度高于靶体阻力

Forrestal等 (Forrestal & Piekutowski 2000, Piekutowski et al. 1999)通过研究钢杆在0.5$\sim$3.0km/s范围内侵彻6061-T6511铝靶, 发现随着撞击速度增大,弹体经历从刚体到侵蚀弹体的转变, 存在3个响应区:刚性弹侵彻、变形非侵蚀弹侵彻和侵蚀弹侵彻.在前两个响应区之间的过渡区出现侵深大幅下降的现象,且不同的杆弹头形、过渡区特征存在明显差异.

Chen和Li(2004)对上述现象进行了理论分析,根据不同侵彻速度和失效机理定义了刚性弹侵彻、半流体侵彻和流体侵彻3个区域,并利用Chen和Li(2002)提出的撞击函数$I$分析确定了刚性弹侵彻和半流体侵彻的临界判据.半流体侵彻的下限$I_{\rm c} $可用撞击函数来表达, 即

$$ I_{\rm c} = \max \left( {I_{\rm c1} ,I_{\rm c2} }\right), \qquad I_{\rm c1} = \dfrac{I_{\rm c2} }{2BN_2 } (1)$$

式中$I_{\rm c2} $为由Alekseevskii-Tate模型推得的半流体侵彻下限,$I_{\rm c1} $为刚性弹侵彻上限, 常数$B \approx 1$, $N_2$为形状参数. 转变区宽度可相应地表达为$\varDelta = \left( {I_{\rm c} - I_{\rm c1} } \right)$. 对于半球头弹体, $N_2 \approx 0.5$,故对于头部比半球头更钝的弹体, $I_{\rm c1} < I_{\rm c2} $,$\varDelta = I_{\rm c2} - I_{\rm c1} > 0$, 如图2(a)所示;反之, 对于尖锥头弹体, $I_{\rm c1} > I_{\rm c2} $, $\varDelta =0$,如图2(b)所示. 由于半流体侵彻深度明显低于刚性弹侵彻, 因此,判定转变速度可以预测弹体最大侵彻深度.

图2   从刚性弹侵彻向半流体侵彻转变 (Chen & Li 2004).(a)直线钝头弹和平头弹, (b)尖锥头弹$(X$为侵彻深度, $d$ 为弹体直径,$L$ 为弹体初始长度, $\rho _{\rm p} $为弹体材料密度, $\rho _{\rm t} $ 为靶体材料密度)

   

此外, Wen等 (Lan & Wen 2010, Lu & Wen 2018, Wen & Lan 2010)从一维长杆高速侵彻模型出发,定义了刚性弹侵彻临界速度$V_{\rm R} $和侵蚀弹侵彻临界速度$V_{\rm H}$, 对长杆弹侵彻的不同模式开展了一系列研究.

实验中也观测到图2(a)所示的现象,钝头弹和平头弹存在一个狭窄的侵彻深度下降的区域,弹体在此区域内大幅凸出和弯折 (Forrestal & Piekutowski 2000). 最近Kong等(2017c)在钢杆侵彻砂浆靶体的实验中发现混凝土类靶体也存在类似的转变现象.Rosenberg和Dekel(2003)通过数值模拟再现了此转变现象,并同时指出考虑弹体失效应变是模拟得到转变点处侵彻深度显著下降的必要条件.徐晨阳等(2018)采用数值模拟分析了弹靶材料特性和弹体头形对转变点的影响.

2.1.2 弹体强度低于靶体阻力

对于强度更大的靶体材料, 随着撞击速度的增加, 将出现由界面击溃 (interfacedefeat)向半流体侵彻的转化. 图3Li等(2015b)定义的长杆撞击陶瓷靶的3种模式, 随着撞击速度 (弹尾速度)的增大,弹头速度 (侵彻速度)出现由零向半流体侵彻速度转变的典型变化.

图3   不同撞击速度下弹头速度与弹尾速度随时间的变化示意图 (Li et al. 2015b). (a) $v_0 \leq v_0^{\rm lower} $, (b) $v_0^{\rm lower} < v_0 < v_0^{\rm upper} $, (c) $v_0 \geq v_0^{\rm upper} $

   

Lundberg等(2000)在分析钨和镆长杆侵彻陶瓷靶时发现了此现象,后续的实验和模拟 (Behner et al. 2011; Anderson & Walker 2005; Andersson et al. 2007; Lundberg & Lundberg 2005;Lundberg et al. 2006, 2013)验证了这一现象. Lundberg等(2000)提出了可能出现该现象的压力范围并得到了转变速度的区间,该转变速度取决于陶瓷靶的材料属性, 且其为小尺寸时受尺寸律影响(Lundberg et al. 2013). Li等(2015b)分析了界面击溃的速度上限与长杆侵彻的速度下限,进而确定了转变速度的范围.对于界面击溃转变速度问题的研究将在后文详细论述.

综上, 随撞击速度增大, 弹体侵彻的模式将发生变化:对于弹体强度高于靶体阻力的情况,将发生刚性弹侵彻、变形非销蚀弹侵彻和半流体侵彻的转化;对于弹体强度低于靶体阻力的情况,则会发生界面击溃向半流体侵彻的转化.

2.2 长杆高速侵彻的4个阶段

Eichelberger和Gehring(1962)基于实验结果提出了高速撞击成坑的4个典型阶段,Christman和Gehring(1966)将它们更清晰地表述为初始瞬态阶段(first/transient phase)、主要侵彻阶段 (primary penetration phase)、次级侵彻阶段 (secondary penetration phase)和靶体回弹阶段(recovery phase), 如图4所示. 此后,研究者们在此基础上开展了细致的研究和深入的讨论 (Anderson & Orphal 2003; Anderson et al. 1992b; He & Wen 2013; Herrmann & Wilbeck 1987; Orphal 1997, 2006; Rosenberg & Dekel 2001a; Tate 1986), 综述如下.

图4   长杆高速侵彻的4个阶段 (Christman & Gehring 1966)

   

2.2.1 初始瞬态阶段

初始瞬态阶段伴随弹体开坑, 仅持续几个微秒, 对应侵彻深度约数倍杆径(Christman & Gehring 1966). Anderson等(1992b)通过模拟认为初始瞬态阶段的作用时间和距离与几何参数和材料属性相关,而与撞击速度无关. 高压力冲击波在界面处产生并在杆和靶中同时传播,到达自由表面反射为卸载波卸载此高压力. 在图4所示的压 力--时间历程图中,初始瞬态阶段表现为一个压力陡峰. 该压力值可由Hugoniot冲击关系给出,仅依赖撞击速度和材料的密度及可压缩性 (Herrmann & Wilbeck 1987).

在高速撞击中, 高压冲击波将导致严重的塑性变形以及融化和汽化. 此外,高温和高压导致的闪光亦在实验中被观测到. 由于涉及多个物理甚至化学过程,对于初始瞬态阶段的解析描述很复杂, 且缺乏其对总侵彻深度影响的准确分析.

2.2.2 主要侵彻阶段

主要侵彻阶段最大的特征就是准静态 (quasi steady-state)侵彻:压力由瞬态阶段的峰值下降为一个恒值, 同时弹靶界面的移动速度(即侵彻速度)也近似为一个常数. 该阶段持续时间由弹体长径比决定.长杆弹具有较大长径比, 因而此阶段作用时间最长,对最终侵彻深度的影响也最为显著.

主要侵彻阶段是所有理论分析模型的核心, 该阶段弹体和靶体均以半流体的方式变形,弹体减速并发生侵蚀, 弹体长度缩短. 如果速度足够大, 弹体将在此阶段完全侵蚀;如果弹体被减速到低于某临界值, 则将转变为刚性侵彻(弹体强度大于靶体强度)或界面击溃 (弹体强度小于靶体强度).

2.2.3 次级侵彻阶段

长杆高速侵彻的第3阶段通常被认为发生在长杆完全侵蚀之后,直至弹坑周围材料的能量密度低至不能克服材料变形阻力 (Christman & Gehring 1966), 该阶段通常被称作次级侵彻阶段或后继流动 (afterflow) (Tate 1986).

在实际侵彻过程中, 次级侵彻通常和主要侵彻阶段同时存在.为区分两阶段的侵彻深度, Orphal(2006)选择速度转折点作为次级侵彻阶段的起始点(对应长杆1.25倍杆径的剩余长度), 而Rosenberg和Dekel(2001a)选择压力曲线的转折点作为起始点.

Orphal(2006)认为此阶段可能存在3种不同机制:首先是弹体速度急速下降, 这一现象对于长径比较小的弹体尤为突出;其次是靶体携带的动能使弹孔进一步扩大, 这一部分被称为后继流动,并与空腔膨胀理论相关联 (Tate 1986); 最后是侵蚀弹体残骸的额外侵彻,需要弹体密度大于靶体密度且速度较高, 以使弹体残骸的速度为正 (Allen & Rogers 1961, Orphal 1997), 即$V_{\rm r} = \left( {2U - V}\right) > 0$.

以上3种机制可能同时存在于长杆高速侵彻的第3阶段, Rosenberg和Dekel(2000)Anderson和Orphal(2003)通过模拟分析了不同机制的单独作用与耦合作用.

目前对长杆高速侵彻的第3阶段的理论描述尚不完善, Tate(1986)针对后继流动提出的经验公式不具备普适性. He和Wen(2013)研究认为,该现象主要由一定冲击条件下弹体侵蚀碎片形成的管状弹体二次撞击造成,并通过能量守恒建立了次级侵彻深度的工程模型.

2.2.4 弹靶回弹阶段

最后是靶体回弹阶段, 弹坑尺寸由于弹性回弹有轻微缩小,同时伴随高温有重结晶现象. 该阶段对总侵彻贡献极小, 通常不予考虑.

3 长杆高速侵彻的研究方法

类似于其他工程研究领域,长杆高速侵彻的研究包括实验研究、理论分析和数值模拟3个方面.由于目前在长杆高速侵彻领域较为活跃的研究小组一般都采用实验、理论和数值模拟相结合的方式开展工作,因此本文不准备将3个方面割裂开来进行综述,仅在本节中对研究方法及其基本结论作简要论述,而在后续章节中对相应研究结果展开讨论.

3.1 实验研究

3.1.1 实验方法与设备

目前长杆高速侵彻实验大多采用直接弹道实验 (direct ballistictest)和小尺寸逆向弹道实验 (small-scale reverse ballistictest)的方法来进行 (Franzen et al. 1997).直接弹道技术最有代表性的是陶瓷抵抗长杆弹侵彻实验中的侵彻深度(depth of penetration, DOP)方法 (Anderson & Royal-Timmons 1997, Hohler et al. 1995),该方法通过对附在陶瓷后的金属靶剩余侵彻深度的精确测量来反映陶瓷靶的抗侵彻能力(如图5所示). 直接弹道实验的优势在于实验尺寸与实际应用更接近,但靶体尺寸过大会导致不能使用 X射线记录时程信息,故每次实验只能得到一个剩余侵彻深度.小尺寸逆向弹道实验则是通过靶体反向撞击弹体,能利用闪光X射线摄影同时记录侵彻过程的时间和空间信息,但是该实验技术对靶体直径有限制, 只能做小尺寸实验 (陈小伟和陈裕泽 2006).

图5   DOP实验示意图 (Franzen et al. 1997)

   

为达到半流体侵彻所需撞击速度 (通常为1.5$\sim $3.0km/s),以上两种实验方法均主要采用一、二级轻气炮作为加速装置.

弹体通常由高密度金属 (钨、贫化铀)及其合金制成, 靶体材料差异较大,从传统金属到陶瓷 (Anderson & Morris 1992; Anderson & Royal-Timmons 1997; Behner et al. 2006; Hohler et al. 1995, Li et al. 2017, Orphal & Franzen 1997; Orphal et al. 1996, 1997;Rosenberg et al. 1995, 1997a; Subramanian & Bless 1995;Subramanian et al. 1995; Westerling et al. 2001)、玻璃 (Anderson & Holmquist 2013; Anderson et al. 2009, 2011a; Behner et al. 2008; Hohler et al. 1993; Orphal et al. 2009)以及混凝土 (Gold et al. 1996, Kong et al. 2017c, Nia et al. 2014)和编织物 (Walker 2001)等复合材料的抗侵彻性能均有实验报道. 对于直接弹道实验,需设计弹托并安装弹托回收装置 (Lundberg et al. 1996);而对于小尺寸逆向弹道实验, 需在靶体外加装密闭装置 (Kong et al.2017c, Subramanian et al. 1995) (如图6所示). 此外, 靶体尺寸(Franzen et al. 1997, Littlefield et al. 1997, Lundberg et al.1996, Rosenberg & Dekel 2000, Rosenberg et al.1997b)、约束形式 (Anderson & Royal-Timmons 1997, Partom & Littlefield 1995, Subramanian & Bless 1995,Westerling et al. 2001)和金属覆盖板 (Anderson & Royal-Timmons 1997, Subramanian & Bless 1995)等也是实验需要特别关注的问题.

图6   小尺寸弹道实验装置示意图 (Subramanian et al. 1995)

   

除部分DOP实验 (Lundberg et al. 1996, Kong et al.2017c)使用高速摄影记录弹坑数据外,目前在长杆高速侵彻实验中最普遍使用的诊断技术为闪光X射线摄影.在小尺寸逆向弹道实验中,可以从X光照片中读出每个瞬时的侵彻深度、弹体剩余长度和弹体碎片长度,其他物理量在此基础上计算即可求得 (Subramanian et al. 1995).

3.1.2 实验结果与经验公式

Christman和Gehring(1966)针对长杆高速侵彻实验提出半经验的侵彻深度公式

$$ P= \left( {L - D} \right)\left( {\dfrac{\rho _{\rm p}}{\rho _{\rm t} }} \right)^{1/ 2} + 2.42D\left( {\dfrac{\rho _{\rm p} }{\rho _{\rm t} }} \right)^{1 /3}\left( {\dfrac{\rho _{\rm p}V^2}{B_{\rm h}^{\max } }} \right)^{1/3} (2) $$

式中总侵彻深度包括主要侵彻阶段和次级侵彻阶段两部分,右端第一项表示主要侵彻阶段持续到杆弹剩余$L/ D \approx 1$时,而第二项则说明次级侵彻部分与弹体动能和靶材最大布氏硬度有关.

Hohler和Stilp(1987)通过对实验数据的拟合发现, 上述公式仅适用于高速(流体)侵彻, 并建议用基于Alekseevskii-Tate模型算出的侵彻效率$P/L$(无量纲侵彻深度,单位长度杆弹的侵彻深度)代替式中的流体动力学极限$\left( {{\rho_{\rm p} } /{\rho _{\rm t} }} \right)^{1/2}$作为主要侵彻阶段的侵彻深度. 此外他们还发现,侵彻效率$P/L$随着长径比$L / D$的增大而减小,该现象后来被称作长径比效应. Anderson等(1995,1996)发现长径比效应在更高速度和更大长径比中依然存在,并根据实验数据拟合出了考虑此效应的经验公式

$$P / L = - 0.209 + 1.044\bar {V} - 0.194\ln \left( {L/ D} \right) (3) $$

式中$\bar {V}= V /{V_0 }$, $V_0 = 1.5$km/s.

除了侵彻深度, 弹坑直径和体积也是实验中值得关注的量. Bierke等(1992)通过拟合实验数据得到了弹坑直径的经验公式

$${D_{\rm c} } /{D_{\rm p} = }1.1524 + 0.3388V_0 + 0.1286V_0^2 (4) $$

Walker等(2001)也得出了类似的经验公式

$${D_{\rm c} }/{D_{\rm p} = }1 + 0.7V_0 (5) $$

Hohler和Stilp(1987)发现低速下弹坑体积与长径比相关,高速下此相关性消失, 弹坑体积正比于弹体动能, 这和他们在短杆$(L/D\approx 1)$高速侵彻中观测到的侵彻深度正比于$V^{2 /3}$相对应.同样的, Hermann和Wilbeck(1987)也发现在超高速撞击中弹坑体积与弹体动能的比值为一个与靶材强度相关(用布氏硬度$B_{\rm h} $表征)的常数.

短粗弹体和长杆弹高速撞击成坑形状有明显差异: 前者弹坑基本呈球形,后者则为狭窄深坑. 对应地,长杆弹侵彻深度在高速下趋近于流体动力学极限$\left( {{\rho _{\rm p}} /{\rho _{\rm t} }} \right)^{1/ 2}$,故提高速度对增加侵彻深度贡献不大;而短粗弹体侵彻深度正比于$V^{2/3}$, 因而没有上限.控制金属球和短杆高速撞击半无限厚靶的侵彻深度的无量纲参数${\rho_{\rm p} V^2} / {B_{\rm h} }$又被称为Best数 (Belyakov et al.1963), 由于Christman和Gehring(1966)认为次级侵彻阶段由杆弹的最后部分$L/ D= 1$造成, 因此式(2)中次级侵彻阶段的侵彻深度主要依赖于Best数和弹/靶密度比.

3.2 数值模拟

数值计算方法根据不同坐标系选取可分为拉格朗日 (Lagrangian)法和欧拉(Euler)法 (Anderson 1987),前者的优势在于追踪材料变形和弹靶界面位移,但在处理大变形问题时容易产生网格畸变以及负体积时有较大误差甚至无法计算;后者能处理侵彻中的弹靶大变形, 但难于追踪材料变形和弹靶界面位移.结合以上两种方法, 发展出了网格以一定速度移动的任意拉格朗日--欧拉法(arbitrary Lagrangian Euler, ALE) (Hirt et al. 1974). 此外,光滑粒子法 (smooth particle hydrodynamics,SPH)能解决拉氏算法的网格畸变并避免网格删除的经验性,常用于高速碰撞的模拟计算. 兰彬(2008)比较了ALE法和SPH法在长杆高速侵彻中的模拟结果,结果认为ALE法在计算负荷和准确性上更优. 由于SPH算法计算效率偏低,进而发展出了自适应网格算法 (Ortiz 1996) (图7(a))与有限元和粒子耦合的算法 (Johnson et al. 2002, Johnson & Stryk 2003) (图7(b)).

图7   不同算法的数值模拟结果.(a)网格自适应算法对WHA长杆侵彻有约束陶瓷靶的模拟结果 (Ortiz 1996),(b)有限元和粒子耦合的算法对钨长杆侵彻钢靶的模拟结果 (Johnson et al. 2002)

   

随着计算机硬件和计算方法快速发展,众多商业软件和专业计算程序被广泛应用于长杆高速侵彻的数值模拟.目前大量模拟工作采用的商业软件有: LS-DYNA, MSC-DYTRAN, AUTODYN,EPIC等, 而专业计算程序中较成功的有三维流体流体动力学程序CTH(McGlaun et al. 1990)和二维欧拉程序PISCES 2DELK (Rosenberg & Dekel 1994a, 1996, 1998, 1999, 2000; Rosenberg et al. 1997a)

材料本构的选择对模拟结果有较大影响.目前在长杆高速侵彻金属靶的模拟中最广泛使用的是Johnson-Cook本构模型(Johnson & Cook 1983), 而在更高的撞击速度下,考虑材料可压缩性和剪切模量的Steinberg模型 (Steinberg 1987,Steinberg et al. 1980, Steinberg & Lund 1989)能更准确地描述冲击波高压状态下的材料特征. 对于脆性材料,需要对裂纹区和粉碎区进行更恰当的模拟.陶瓷靶材需要分别对完善材料和粉碎区失效材料的压缩强度进行描述,并引入在0到1之间变化的损伤函数. JH模型 (Holmquist & Johnson 2005, 2011; Johnson & Holmquist 1994)是目前使用最广泛的陶瓷本构模型, 此外还有Wilkins模型 (McGlaun et al. 1990, Walker & Anderson 1991)、Rajendran-Grove(RG)模型 (Rajendran 1994, Rajendran & Grove 1996)和Deshpande-Evans (DE)模型 (Deshpande & Evans 2008).混凝土靶则主要采用考虑应变率效应和体积压缩的HJC模型 (Holmquist et al. 1993)及其改进模型 (Islam et al. 2013, Kong et al. 2016a, Liu et al. 2009, Polanco-Loria et al. 2008, Tu & Lu 2010)以及考虑不同表面强度和损伤函数的K & C模型 (Malvar et al.1997)及其改进模型 (Kong et al. 2017a, Weerheijm & VanDoormaal 2007).

近年来长杆高速侵彻领域的数值模拟研究主要集中在以下几个方面:弹靶材料参数对侵彻深度的影响 (Anderson et al. 1992b, 1993, 1999a;Forrestal & Longcope 1990; Kong et al. 2017b; Li et al.2015a; Rosenberg & Dekel 1998, 2000, 2001b, 2004),长径比效应 (Anderson et al. 1995, 1996; Orphal et al. 1993, 1995;Rosenberg & Dekel 1994a; Walker 1999), 侵彻末段作用机理(Anderson & Orphal 2003; Orphal 1997; Rosenberg & Dekel 2000, 2001a), 陶瓷靶抗长杆侵彻机理 (Li et al. 2017;Rosenberg et al. 1995, 1997b, 1998; Zhang et al. 2011; 蒋东等 2010; 谈梦婷等 2016).大量数值模拟工作都与实验结果和理论分析相互印证以期具有说服力.

4 长杆高速侵彻的理论模型

理论分析基于对实验和模拟所得到的结果与现象的分析和认识, 进行抽象和近似,进而建立具有简单数学表达的物理模型,能反映实验和模拟中观察到的典型物理特征并具有一定的预测能力.长杆高速侵彻的理论模型经历了从早期简单的流体动力学理论到经典的Alekseevskii-Tate模型再到更复杂模型的发展,各模型提出均基于对侵彻机理的认知, 其适用性得到了大量实验和数值模拟的验证.

4.1 流体动力学理论与Allen-Rogers模型

长杆高速侵彻最早的理论模型源自分析高速射流的流体动力学理论 (hydrodynamictheory of penetration, HTP). Brikhoff等(1948)将金属射流视作高速流体,碰撞产生极高压力导致分析时忽略射流和靶体强度. 假设射流侵彻为定常过程,沿中心线射流/靶体界面压力平衡关系即可用Bernoulli方程描述为

$$ \dfrac{1}{2}\rho _{\rm p} \left( {V - U} \right)^2 =\dfrac{1}{2}\rho _{\rm t} U^2 (6) $$

式中,$V$和$U$分别为射流速度和侵彻速度, $\rho _{\rm p} $和$\rho _{\rm t}$分别为射流密度和靶体密度, 定义密度比$\mu = \sqrt {{\rho _{\rm t}} / {\rho _{\rm p} }} $, 则侵彻速度可表示为

$$ U = \dfrac{V}{1 + \mu } (7) $$

由定常假设, $V$和$U$以及射流消蚀速率$\left( {V - U}\right)$均为常数, 无量纲侵彻深度可表示为

$$ \dfrac{P}{L}= \dfrac{U}{V - U} = \dfrac{1}{\mu } (8) $$

式中, $1/ \mu $为长杆的“流体动力学极限”. 由于形式简单,流体动力学理论可为快速检验定常侵彻速度和侵蚀速率提供合理近似,其应用也从最初的金属射流延伸到了长杆高速侵彻. 式(8)还说明,在较高速度下增大撞击速度对提高侵彻深度贡献不大,这一特点与刚性长杆增大撞击速度即获得更高侵彻深度的特性有本质差异.虽然杆弹和靶体均有强度, 但强度效应在高速下近似可忽略,进而流体动力学理论在长杆高速侵彻中可用.

在流体动力学理论的基础上, Allen和Rogers(1961)在Bernoulli方程中加入强度项以描述长杆高速侵彻

$$ \dfrac{1}{2}\rho _{\rm p} \left( {V - U} \right)^2 =\dfrac{1}{2}\rho _{\rm t} V^2 + \sigma (9) $$

式中$\sigma$与靶材强度相关, 其值约为靶材动态压缩强度的3倍 (Rosenberg & Dekel 2012) 由式(9)可解出侵彻速度为

$$ U = \dfrac{V - \sqrt {\mu ^2V^2 + 2\left( {1 - \mu^2} \right)\sigma / {\rho _{\rm p} }} }{1 - \mu ^2} (10) $$

将$U = 0$代入式(10), 可得侵彻开始发生的临界速度$V_{\rm c} = \sqrt{{2\sigma } /{\rho _{\rm p} }} $, 临界速度与靶材密度无关.

对时间积分可求得无量纲侵彻深度的表达式

$$ \dfrac{P}{L} = \dfrac{U}{V - U} = \dfrac{V - \sqrt{\mu ^2V^2 + 2\left( {1 - \mu ^2} \right)\sigma / {\rho _{\rm p}}} }{\sqrt {\mu ^2V^2 + 2\left( {1 - \mu ^2} \right)\sigma/{\rho_{\rm p} }} - \mu ^2V} (11)$$

若忽略强度项$\sigma $, 式(10)和式(11)可分别退化为式(7)和式(8).

Allen和Rogers(1961)分别用由金、铅、铜、锡、铝和镁制成的杆弹高速撞击铝圆柱,实验结果与模型预测对比发现, 模型能成功解释除金杆外的实验数据, 如图8所示, 在高速下靶材强度影响变得不重要, 实验数据趋近流体动力学极限.

图8   实验数据与流体动力学理论的对比 (Allen & Rogers 1961)

   

Allen和Rogers(1961)把金杆具有较大侵彻深度的现象归因于次级侵彻,认为侵蚀弹体残骸将在主要侵彻阶段结束后继续侵彻靶体.侵蚀弹体残骸速度定义为$V_{\rm r} = 2U - V$, 当$V_{\rm r} > V_{\rm c} $时发生次级侵彻. 若弹靶密度相近, $V_{\rm r} $远小于$U$和$V$;而在高密度金杆撞击低密度铝靶时, $V_{\rm r} $不可忽略.为验证上述推论, 近似地将侵彻速度取为流体动力学极限 (即式(7)), 可得

$$V_{\rm r} = \dfrac{1 - \mu }{1 + \mu }V (12) $$

若弹密度低于靶密度, 即$\rho _{\rm p} < \rho _{\rm t} $, $\mu > 1$,则$V_{\rm r} < 0$, 残骸反向流动; 反之, $V_{\rm r} > 0$,残骸正向侵彻. 若弹靶密度相近, 则$\mu \to 1$, $V_{\rm r} \to 0$;若弹密度远高于靶密度, 则$\mu \to 0$, $V_{\rm r} \to V$.

Orphal和Anderson(1999)在逆向弹道实验中运用闪光X射线摄影观测到了侵蚀弹体残骸的侵彻,残骸长度和弹体初始长度与剩余长度之差近似相等.

流体动力学理论最大的不足在于未考虑材料强度,虽然在此基础上改进的Allen-Rogers模型引入了靶体强度,但由于模型中的定常状态和不可压流体的两个假设,实验结果与模型预测仍存在偏差. Anderson和Orphal(2008)利用逆向弹道实验数据和基于CTH程序的模拟结果与流体动力学理论模型进行对比,发现在高达4km/s的速度下实验和模拟的结果仍明显低于模型预测,且在4km/s时材料强度依然存在. Anderson 和Orphal (Anderson & Orphal 2008, Orphal 2006, Orphal & Anderson 1999)通过模拟证实了不可压流体假设对模型预测的影响,随着撞击速度的提高, 可压缩性的影响增加.虽然部分实验结果与流体动力学理论预测接近, 但Orpha(2006)认为这是由于模型的过高预测和模型未考虑的第3阶段侵彻相抵消的结果.若考虑定常侵彻外还包含第3阶段侵彻,更高速度下总侵彻深度应该超过流体极限.

4.2 Alekseevskii-Tate模型

Alekseevskii-Tate模型是长杆高速侵彻最为经典的理论模型,除了应用于典型的长杆高速正侵彻半无限厚金属靶的研究,其应用范围还延伸到了陶瓷靶等多种靶材、有限厚靶体、非理想长杆侵彻.本小节将简要概述模型假设和控制方程, 介绍模型的近似解,并对模型有效性进行评述.

4.2.1 模型概述

Alekseevskii(1966)Tate(1967,1969)几乎同时且各自独立地给出了更完备的长杆弹高速 (半流体)侵彻的 理论模型,在Bernoulli方程中加入弹靶的强度项进行修正. 该模型假设弹体在侵彻过程中呈刚性,仅在靠近弹靶界面的薄层发生侵蚀, 呈半流体状 (如图1所示).在弹靶接触面上应力平衡且速度连续, 弹头速度即为侵彻速度,同时由弹体的流动应力控制弹体减速. 其控制方程组如下

$$ \dfrac{1}{2}\rho _{\rm p} \left( {v - u} \right)^2 +Y_{\rm p} = \dfrac{1}{2}\rho _{\rm t} u^2 + R_{\rm t} (13)$$

$$ \rho _{\rm p} l'\dfrac{{\rm d}v}{{\rm d}t} = - Y_{\rm p} (14) $$

$$ \dfrac{{\rm d}l'}{{\rm d}t} = - \left( {v - u} \right) (15)$$

$$\dfrac{{\rm d}p}{{\rm d}t} = u (16) $$

式中$\rho _{\rm p} $和$\rho _{\rm t} $分别为弹材和靶材密度;$Y_{\rm p} $为弹体强度; $R_{\rm t} $为靶体侵彻阻力; $u$, $v$,$p$和$l'$分别为侵彻 (弹头)速度、弹体(弹尾)速度、侵彻深度和弹体剩余长度, 四者均随时间$t$变化,故均用小写表示某时刻的值.

由式(13)可直接推得

$$ u = \dfrac{v - \sqrt {\mu ^2v^2 + \left( {1 - \mu ^2}\right)V_{\rm c} ^2} }{1 - \mu ^2} (17) $$

式中$\mu = \sqrt{{\rho _{\rm t} }/{\rho _{\rm p} }} $为弹靶密度比, $V_{\rm c} =\sqrt {{2\left| {R_{\rm t} - Y_{\rm p} } \right|} / {\rho _{\rm p}}} $为弹尾临界速度, 仅当弹体初始撞击速度$v_0 > V_{\rm c} $时,才能发生长杆半流体侵彻.

在侵彻末端, 对应不同弹靶强度组合, 有以下两种情形: 若$R_{\rm t} >Y_{\rm p} $, 当弹体速度下降至$V_{\rm c} $时, 侵彻速度$u = 0$,弹体不能侵彻靶体; 若$R_{\rm t} < Y_{\rm p} $,弹体速度下降至${V_{\rm c} } /\mu $, $u = v$,剩余弹体以刚性弹继续侵彻.

弹靶强度项$Y_{\rm p} $和$R_{\rm t}$取值是Alekseevskii-Tate模型的重点和难点, 后文将对此进行详细讨论.

4.2.2 模型近似解

Alekseevskii-Tate方程组求解通常由Tate(1967,1969)得到的理论解直接数值积分或采用由Walters和Segletes (Segletes & Walters 2003, Walters & Segletes 1991)发展出的精确解. 但是, 由于方程组的非线性, 弹体(弹尾)速度、侵彻速度、弹体长度和侵彻深度关于时间函数都是隐式的,最终仍需数值求解. Forrestal等(1988)Walters等(2006)先后推导了无量纲Alekseevskii-Tate方程组的一阶和三阶摄动解,得到了上述物理量关于时间的显式表达. 其中, Forrestal等(1988)的一阶摄动解仅适用于低强度靶, 且与数值解的吻合时间相对较短;Walters等(2006)同时考虑弹靶强度,发展出了适用于高强度靶的一阶和三阶摄动解,并结合算例分析说明了三阶摄动解比一阶摄动解更贴近数值解.由于摄动解尤其是三阶摄动解的数学表达相当复杂,且无法准确给出侵彻末端的情况, 并不适用于工程应用.

Jiao和Chen(2018)在对Alekseevskii-Tate模型中剩余弹体相对长度的对数表达式进行线性近似的基础上,获得如下两组显式的理论解析解:

(1) 近似解1

$$ \dfrac{v}{v_0 } = 1 + \dfrac{2\bar {\mu }}{\varPhi _{\rm Jp}K}\ln \left(1 - \dfrac{K}{2\bar {\mu }}\dfrac{t}{\tau }\right) (18)$$

$$\dfrac{u}{v_0 } = \dfrac{1}{1 + \mu } \left( {1 + \dfrac{2\bar{\mu }}{\varPhi _{\rm Jp} K}\ln (1 - \dfrac{K}{2\bar {\mu }}\dfrac{t}{\tau })} \right) - \dfrac{1}{2\mu } v_{\rm c\ast } ^2 (19) $$

$$l' = L - \dfrac{\mu v_0 }{1 + \mu }\left[ {\left( {1+ \dfrac{1 + \mu }{2\mu ^2}v_{\rm c\ast }^2 - \dfrac{2\bar {\mu}}{\varPhi _{\rm Jp} K}} \right)t + \dfrac{2\bar {\mu }}{\varPhi_{\rm Jp} K}\ln (1 - \dfrac{K}{2\bar {\mu }} \dfrac{t}{\tau})\left( {t - \dfrac{2\bar {\mu }}{K}\tau } \right)} \right] (20) $$

$$ p = \dfrac{v_0 }{1 + \mu }\left[ {\left( {1 -\dfrac{1 + \mu }{2\mu }v_{\rm c\ast }^2 - \dfrac{2\bar {\mu}}{\varPhi _{\rm Jp} K}} \right)t + \dfrac{2\bar {\mu }}{\varPhi_{\rm Jp} K}\ln (1 - \dfrac{K}{2\bar {\mu }} \dfrac{t}{\tau})\left( {t - \dfrac{2\bar {\mu }}{K}\tau } \right)} \right] (21) $$

(2) 近似解2

$$ \dfrac{v}{v_0 } = \dfrac{\mu K - \bar {\mu}v_{\rm c\ast }^2 }{2\mu \left( {1 - \mu } \right)} (22)$$

$$ \dfrac{u}{v_0 } = \dfrac{\left[ {\mu K - \bar {\mu}\left( {1 + \mu } \right)v_{\rm c\ast }^2 } \right]}{2\mu ^2\bar{\mu }} (23) $$$$l' = L - \dfrac{Kv_0 }{2\bar {\mu }}t (24) $$

$$p = \dfrac{\left[ {\mu K - \bar {\mu }\left( {1 + \mu} \right)v_{\rm c\ast }^2 } \right]v_0 }{2\mu ^2\bar {\mu }}t (25)$$

其中, $v_{\rm c\ast } = {V_{\rm c} }/ {v_0 }$是弹尾相对临界速度,$\mu = \sqrt {{\rho _{\rm t} } / {\rho _{\rm p} }} $和$\bar {\mu }= {\left( {1 - \mu ^2} \right)} / \mu$是与弹靶密度比相关的两个无量纲参数, $\varPhi _{\rm Jp} = {\rho_{\rm p} v_0^2 } / {Y_{\rm p} }$是Johnson破坏数, $\tau = L/{v_0}$为一个特征时间. 此外, $K$定义为一个无量纲线性系数,其取值依据是令弹体剩余长度$l'$在初始时刻$t = 0$(自动满足)和终态时刻$t = T$ (其中终态时刻近似取为$T= \tau \cdot{2\bar {\mu }} / K)$均分别相等, 无量纲线性系数的表达式为$$K = 1 - \mu + \dfrac{\bar {\mu }}{\mu } \dfrac{v_{\rm c\ast }^2}{2} + \sqrt {\left( {1 - \mu + \dfrac{\bar {\mu }}{\mu } \dfrac{v_{\rm c\ast }^2 }{2}} \right)^2 - \dfrac{4\bar {\mu}\left( {1 - \mu } \right)}{\varPhi _{\rm Jp} }} (26) $$值得说明的是, 由于无量纲线性系数取值,式(20)与式(24)及式(21)与式(25)在$t = 0$和$t =T$时刻对应的值均相等,即近似解1和近似解2得到的剩余弹体长度和侵彻深度在长杆侵彻初、终态时刻的值都一致.

Jiao和Chen(2018)进一步分析发现, Walters等(2006)得到的一阶摄动解仅是近似解1在高速撞击条件下的特殊形式.通过详细比较理论解与两组近似解的区别与适用范围,可获得若干物理意义明确的推论. 在图9所示的两组从撞击速度到弹靶参数均不同的算例分析中,近似解1都比一阶摄动解更接近Alekseevskii-Tate模型的理论解,是更推荐使用的一组解; 而近似解2给出了定常的弹尾速度和侵彻速度, 形式更加简单,可应用于长杆侵彻的定性分析和快速预测.

图9   不同算例中两组近似解、一阶摄动解与理论解对比 (Jiao & Chen 2018)

   

4.2.3 模型有效性

Alekseevskii-Tate模型的成功,在于它能反映长杆高速侵彻实验数据的若干特征: 在兵器速度范围(0.8$\sim $1.8km/s)内,无量纲侵彻深度随撞击速度的增大急剧上升,而在更高速度下趋近于流体动力学极限; 侵彻效率受密度影响严重,强度影响在更高速度下逐渐消失. Hohler和Stilp(1987)及Anderson等(1992a)搜集了大量长杆弹高速撞击金属靶的实验数据, 总结出上述规律.但他们同时也发现,模型不能解释实验观察到的侵彻效率随着长径比增大而减小的现象,即长径比效应. 这一现象将在第6节进行讨论.

传统实验基于撞击条件与最终结果的关系来分析模型有效性,而数值模拟提供从时间历程上检验侵彻过程的手段 (Anderson 2003).Anderson和Walker(1991)通过对$L /D=10$钨合金杆以1.5km/s速度撞击装甲钢靶的数值模拟并与Alekseevskii-Tate模型预测结果进行对比. 如图10所示,两者差异主要存在于侵彻初期和侵彻末端:模型不能反映侵彻初期的瞬时高压及导致的高侵彻速度; 在侵彻末端,模型预测的减速比模拟结果更晚且更迅速; 模型预测弹体完全侵蚀,而模拟和实验结果都表明弹坑底部留有残余杆弹.上述偏差是因为模型仅针对长杆高速侵彻的准静态阶段,模型的强度参数源于对实验数据反向拟合, 可看作是一种平均化结果.

图10   数值模拟与Alekseevskii-Tate模型预测的对比 (Anderson & Walker 1991)

   

综上, 模型预测与实验/模拟结果差异主要来源于初始瞬态和侵彻末端,一维准静态假设的Alekseevskii-Tate模型无法描述上述行为. 此外,模型无法反映实验中观测到的长径比效应.

4.3 其他理论模型

在Alekseevskii-Tate模型基础上, 国内外学者提出了诸多改进的理论分析模型,其中较有代表性的有:Rosenberg-Marmor-Mayseless模型、Walker-Anderson模型、Zhang-Huang模型、Lan-Wen模型和Kong模型.

4.3.1 Rosenberg-Marmor-Mayseless模型

Rosenberg等(1990)注意到侵彻过程中弹靶界面压力从长杆弹头部中心向弹坑边缘的衰减,将压力沿界面的积分替换为中心压力和“等效截面积”.通过引入弹体刚性部分等效截面积$A_{\rm p}$和蘑菇头部分等效截面积$A_{\rm t} $, 弹靶界面两侧压力平衡方程即为

$$A_{\rm p} \left[ {\dfrac{1}{2}\rho _{\rm p} \left( {v- u} \right)^2 + Y_{\rm p} } \right] = A_{\rm t} \left({\dfrac{1}{2}\rho _{\rm t} u^2 + R_{\rm t} } \right) (27) $$

杆长变化方程、弹体减速方程和侵彻深度方程同Alekseevskii-Tate模型,故式(27)和式(14)$\sim$式(16)即构成Rosenberg-Marmor-Mayseless模型.

在参数选取方面, Rosenberg等(1990)建议等效截面积的比值$S \equiv{A_{\rm t} } /{A_{\rm p} }= 2$, $Y_{\rm p}$取为弹材Hugoniot弹性极限, $R_{\rm t}$由静态柱形空腔膨胀理论计算得$$R_{\rm t} = \dfrac{\sigma _{\rm yt} }{\sqrt 3 }\left[ {1 + \ln\dfrac{\sqrt 3 E_{\rm t} }{\left( {5 - 4\nu } \right)\sigma _{\rm yt} }} \right] (28) $$

Rosenberg-Marmor-Mayseless模型通过引入等效截面积, 粗略考虑了二维效应.模型预测与钢杆和钨杆侵彻不同强度厚钢靶的实验结果吻合较好 (Rosenberg et al.1990), 但模型中等效截面积需经验性确定, 导致模型预测能力受限.

4.3.2 Walker-Anderson模型

Walker和Anderson(1995)基于钨合金杆撞击装甲钢靶的数值模拟结果(Anderson & Walker 1991),通过假定弹/靶中压力场和速度场分布,建立一个时间相关的长杆高速侵彻模型. 通过参数简化处理,弹靶界面两侧应力平衡方程可表示为$$\dfrac{1}{2}\rho _{\rm p} \left( {v - u} \right)^2 + \sigma _{\rm yp} = \dfrac{1}{2}\rho _{\rm t} u^2 + \dfrac{7}{3}\ln \left(\alpha \right)\sigma _{\rm yt} (29) $$杆长变化方程、弹体减速方程和侵彻深度方程同Alekseevskii-Tate模型.通过比较式(29)和式(13)可以看出,Alekseevskii-Tate模型中的弹体强度项$Y_{\rm p}$被替换为弹材动态屈服强度$\sigma _{\rm yp} $, 而靶体阻力$R_{\rm t}$同样与靶材的动态屈服强度$\sigma _{\rm yt} $相关, 即

$$R_{\rm t} = \dfrac{7}{3}\ln \left( \alpha\right)\sigma _{\rm yt} (30) $$

其中, $\alpha$为靶体内塑性区无量纲长度, 由可压缩材料柱状空腔膨胀理论计算得, 即

$$ \left( {1 + \dfrac{\rho _{\rm t} u^2}{\sigma _{\rm yt} }} \right)\sqrt {K_{\rm t} - \rho _{\rm t} \alpha ^2u^2} =\left( {1 + \dfrac{\rho _{\rm t} \alpha ^2u^2}{2G_{\rm t} }}\right)\sqrt {K_{\rm t} - \rho _{\rm t} u^2} (31) $$

其中$K_{\rm t} $和$G_{\rm t} $分别为靶材的体积模量和剪切模量.由于侵彻速度$u$随时间变化, 导致$\alpha$表征的靶体内塑性区范围也随时间变化, 故$R_{\rm t}$在侵彻过程中亦随时间变化. 此外,该模型还考虑了弹靶初始撞击产生的瞬态高压,初始瞬态阶段的侵彻速度$u$由弹靶材料的冲击压缩Hugoniot关系得到(Walker & Anderson 1995).

Walker-Anderson模型综合考虑了初始瞬态阶段和塑性区范围,随速度变化的侵彻阻力更符合实际侵彻历程. 模型预测与实验结果非常吻合(Walker & Anderson 1995),但模型过于复杂导致不适用于工程应用,部分参数依赖模拟结果因而预测能力有限.

4.3.3 Zhang-Huang模型

Zhang和Huang(2004)假设长杆弹在侵彻过程中头部形状为半球形,基于动态空腔膨胀理论求得弹靶界面的平均压力, 界面轴向应力平衡方程为$$2\rho _{\rm p} \left( {v - u} \right)^2 + Y_{\rm p} = \left({\dfrac{D}{D_{\rm p} }} \right)^2\left( {R_{\rm t} + \dfrac{\beta }{2}\rho _{\rm t} u^2} \right) (32) $$其中, $D$和$D_{\rm p} $分别为弹孔直径和杆弹直径, Zhang和Huang(2004)建议取$D / {D_{\rm p} }= \sqrt 2 $; $\beta$为动态空腔膨胀压力系数, 对于钢和铝等常见的装甲材料$\beta $在$1\sim 1.5$之间.杆长变化方程、弹体减速方程和侵彻深度方程同Alekseevskii-Tate模型.

可以看到,Zhang-Huang模型其实是在Rosenberg-Marmor-Mayseless模型的基础上将确定靶体阻力的静态空腔膨胀模型替换为动态空腔模型,模型引入了弹孔直径, 同样需要经验性的确定.

4.3.4 Lan-Wen模型

Lan和Wen(2010)通过在靶体内划分不同的响应区,并假设靶体中的速度场分布, 建立了改进的长杆侵彻一维模型.从弹靶界面沿侵彻方向, 靶体可分为流动区、塑性区和弹性区,流动区内材料视作无黏流体, 用修正的Bernoulli方程描述,塑性区和弹性区内材料行为用空腔膨胀模型描述.假设存在一个临界侵彻速度$U_{\rm F0} $, 当$u < U_{\rm F0} $时,靶体内不存在流动区, 此时可由空腔膨胀理论得到

$$\dfrac{1}{2}\rho _{\rm p} \left( {v - u} \right)^2 +Y_{\rm p} = S+C\rho _{\rm t} u^2 (33) $$

其中,$S$为靶体静阻力, $C$为动阻力系数 (对于不可压材料通常取1.5). 当$u\geq U_{\rm F0} $时,考虑侵彻轴线上流动区和塑性区界面两侧的应力平衡, 有

$$ \dfrac{1}{2}\rho _{\rm p} \left( {v - u} \right)^2 +Y_{\rm p} = \dfrac{1}{2}\rho _{\rm t} \left( {u - \delta \left( u\right)} \right)^2+S+C\rho _{\rm t} \delta \left( u \right)^2 (34) $$

其中, $\delta \left( u\right)$为流动区与塑性区界面上的质点速度, $\delta \left( u\right)$随侵彻速度$u$的增大而减小, $\delta \left( {u = U_{\rm F0}} \right) = U_{\rm F0} $, $u \to \infty $时$\delta \left( u\right) \to 0$. 根据上述假设, Lan和Wen(2010)给出的$\delta \left(u \right)$的形式如下

$$\delta \left( u \right) = U_{\rm F0} \exp \left[ { -\left( {\dfrac{u - U_{\rm F0} }{nU_{\rm F0} }} \right)^2} \right] (35)$$

其中, $n$为可调系数, 且有$n \geq 2\sqrt C $; 对于金属靶,临界侵彻速度取为$U_{\rm F0} = \sqrt {{HEL} / {\rho _{\rm t} }} $.

通过假定临界侵彻速度$U_{\rm F0} $,式(33)和式(34)分别建立了高速和低速下的应力平衡方程, 且当$u \to\infty $时,式(34)可退化为与Alekseevskii-Tate模型中应力平衡方程相同的形式,其他方程同Alekseevskii-Tate模型.

Lan-Wen模型首次给出了弹靶界面出现流动区的条件,即弹靶界面上剪应力远小于静水压时材料行为由强度控制转变为静水压控制,并建立了高速侵彻与空腔膨胀理论之间的联系.特别针对弹体强度大于靶体阻力的情况,Lan-Wen模型可描述刚体侵彻、变形体侵彻和消蚀侵彻3种不同长杆弹侵彻模式的相互转化(Lu & Wen 2018, Wen & Lan 2010).通过对临界侵彻速度和式(35)的合理取值,Lan-Wen模型与不同弹靶组合的实验结果吻合较好.

4.3.5 Kong模型

Kong等(2017b)在动态空腔膨胀理论中采用Murnaghan高压状态方程描述压力--体积应变关系, 分别建立了金属类靶体和混凝土类靶体的阻力模型.通过在靶体阻力中加入速度一次项, 靶材的黏性等一般性质得以考虑,从而能更准确描述混凝土和陶瓷材料的应力状态.

代入阻力模型, 金属类靶体和混凝土类靶体的弹靶界面应力平衡关系分别为

$$\dfrac{1}{2}\rho _{\rm p} \left( {v - u} \right)^2 +Y_{\rm p} = AY+B\sqrt {\rho _{\rm t} Y} u/2+C\rho _{\rm t} {u^2}/3 (36) $$

$$\dfrac{1}{2}\rho _{\rm p} \left( {v - u} \right)^2 +Y_{\rm p} = \bar {N}_0 Af_{\rm c} + \bar {N}_1 B\sqrt {\rho _{\rm t} f_{\rm c} } u+\bar {N}_2 C\rho _{\rm t} u^2 (37)$$

两式中, 杆体强度$Y_{\rm p} $取为动态弹性极限$\sigma _{\rm yd}{\left( {1 - \nu } \right)} / {\left( {1 - 2\nu } \right)}$, $A$,$B$和$C$均为无量纲常数. 在描述金属类靶的式(36)中,屈服应力$Y$取靶体平均动态屈服强度$\sigma _{\rm yd} $.在描述混凝土类靶的式(37)中, $f_{\rm c} $为靶材单轴压缩强度; $\bar{N}_0 $, $\bar {N}_1 $和$\bar {N}_2 $为无量纲弹头形状参数,对于平头弹有$\bar {N}_0 = \bar {N}_1 = \bar {N}_2 = 1$,对于半球头弹有$\bar {N}_0 = 1$, $\bar {N}_1 = 2/3$, $\bar {N}_2 =1/ 2$.杆长变化方程、弹体减速方程和侵彻深度方程同Alekseevskii-Tate模型.

Kong模型与其他理论模型最大的不同之处在于, 模型中包含的一般阻力项(速度一次项)能反映靶材黏性. 实际上, Chen等(2008)的分析已指出,靶体阻力中的速度一次项和加速度项能分别反映材料的黏性效应和应变率效应. 因此,在将阻力表达为速度的各次方之和, 物理意义明确.

由于模型参数能先于实验获得, 故具有不错的预测能力.部分金属类靶的侵彻实验结果与模型预测吻合较好,但混凝土类靶实验数据缺乏因而说服力不够. 再者,金属类靶侵彻模型对头形因素考虑较粗糙,而混凝土类靶侵彻模型则直接使用了刚性弹侵彻中的头部形状因子. 此外,靶体阻力与侵彻速度关系的确定仍具有经验性, 需要更多实验和模拟的验证.

5 弹靶材料性质对长杆高速侵彻的影响

从本节开始将详细论述长杆高速侵彻的突出问题,其中部分研究成果已有相应工程应用, 而不少仍是领域内的研究热点.

影响长杆高速侵彻的弹靶材料因素主要有弹材密度、靶材密度、弹体强度和靶体阻力.早期对实验数据的分析认为, 弹靶密度对长杆侵彻的影响远大于强度(Hohler & Stilp 1987), 这与流体动力学模型相契合.随后的研究发现, 弹靶强度对侵彻作用的影响不能忽视,这也直接导致了加入强度项的Alekseevskii-Tate模型及其改进模型的诞生,模型中强度项$R_{\rm t} $和$Y_{\rm p}$的取值一直是分析的重点和难点.

5.1 长杆高速侵彻中的靶体阻力$R_t $

在以Alekseevskii-Tate模型为代表的半流体模型中, 靶体阻力$R_{\rm t}$的取值方法大致可分为三类:(1)将侵彻深度数据带回理论分析模型反向拟合;(2)通过模拟获得相应位置的瞬时压力,再对时间积分或位置积分获得平均化的压力;(3)用在刚性弹侵彻中广泛使用的空腔膨胀理论进行推导.

5.1.1 靶体阻力$R_t $与空腔膨胀理论

Tate(1967)最初建议将$Y_{\rm p} $取为弹材的Hugoniot弹性极限

$$HEL= \dfrac{1 - \nu }{1 - 2\nu }\sigma _{\rm yp} (38)$$

其中, $\sigma _{\rm yp} $为杆材的动态屈服强度, $\nu $为泊松比;$R_{\rm t} $则取为靶材弹性极限$HEL$的3.5倍. 通过对实验数据的拟合,Tate(1986)重新评估了$Y_{\rm p} $和$R_{\rm t} $取值

$$ Y_{\rm p} = 1.7\sigma _{\rm yp} , \qquad R_{\rm t} =\sigma _{\rm yt} \left( {\dfrac{2}{3} + \ln \dfrac{0.57E_{\rm t}}{\sigma _{\rm yt} }} \right) (39) $$

式中$E_{\rm t}$为靶材杨氏模量, $\sigma _{\rm yp} $和$\sigma _{\rm yt}$分别为杆材和靶材动态压缩屈服强度, 此强度与材料布氏硬度相关$\sigma_{\rm y} = 4.2BHN$.

Rosenberg等(1990)Tate(1986)所用球形空腔替换为柱形空腔,所得靶体阻力式(28)与式(39)略有差异.

需要说明的是, 上述取值仅针对金属材料. 金属靶体内,材料响应区域划分为塑性区、弹性区和未变形区; 对于陶瓷等脆性材料,靶体内材料变形可划分为粉碎区、裂纹区和弹性区;而混凝土靶在长杆高速侵彻下的响应区由内向外可划分为密实区、孔隙压实区、开裂区和弹性区(李志康和黄风雷 2010).

Forrestal和Longscope(1990)针对陶瓷靶推导出了理想塑性材料球形空腔膨胀所需的准定常压力$R_{\rm t} $. Anderson和Walker(1991)认为上述取值方法缺乏先验性,只能作为简单近似. 此外他们通过对动量方程沿对称中线积分,获得的$R_{\rm t} $和$Y_{\rm p}$均包含一个剪应力梯度沿响应区的积分项.

Rosenberg和Dekel(1994b)通过对强度为0,长径比为20的不同材质杆弹撞击钢和钨合金靶的模拟发现,靶体阻力$R_{\rm t} $与弹靶密度皆无关系, $R_{\rm t}$与靶材屈服强度$Y_{\rm t} $之间的关系近似符合空腔膨胀理论

$$ R_{\rm t} = A Y_{\rm t} \left( {1 +\dfrac{1}{2}\ln \dfrac{2E_{\rm t} }{3Y_{\rm t} }} \right) (40)$$

其中参数$A$是撞击速度的函数. 上述关系与数值模拟存在参数上的差异,Rosenberg和Dekel(1994b)认为这种差异是因为球形空腔膨胀只能近似处理长杆半流体侵彻,更合理的阻力模型应包括对称轴上的阻力加上其他因素导致的阻力衰减.

实际上, 长杆高速侵彻靶体阻力$R_{\rm t}$显著高于刚性杆侵彻靶体阻力, Rosenberg和Dekel(2010)通过数值模拟否认两者相同的直觉假设,两者靶材料流动状况不同导致了靶体阻力差异. Rosenberg和Dekel(2008)的模拟结果表明, 长杆高速侵彻的靶体阻力约为刚性杆侵彻的 1.3倍. 此外, 其模拟结果还显示了靶体阻力与靶材流动情况的依赖关系,半球空腔表面受载的临界压力$P_{\rm c}$值接近长杆高速侵彻的靶体阻力$R_{\rm t} $,两者数值上的匹配可用靶材流场的相似性加以说明. 图11显示的是强度为1.0GPa的钢靶在铜长杆以2.0km/s侵彻下的弹坑周围和常值内压作用于半球空腔附近的速度场,图中几何尺寸和速度分布均有明显相似性.

图11   长杆侵彻弹坑周围和受内压半球腔附近的速度场 (Rosenberg & Dekel 2008)

   

5.1.2 靶体阻力$R_t $与撞击速度

通过对侵彻深度反向拟合, Anderson等(1992b)发现靶体阻力与长径比和撞击速度均有关系, 其中速度影响尤为突出. 图12即是Anderson等(1993)根据不同实验结果反向拟合得到的靶体阻力随撞击速度的变化曲线.

图12   硬钢的靶体阻力随长杆撞击速度的变化情况 (Anderson et al. 1993)

   

由于实验和模拟均表现出靶体阻力$R_{\rm t} $在侵彻过程中的剧烈变化,为了与最终的侵彻深度契合, Alekseevskii-Tate模型中的$R_{\rm t}$应取侵彻过程中的平均值.

Anderson等(1993)详细比较了用侵彻深度反向拟合的理论模型中的靶体阻力$R_{\rm t}$和对应的数值模拟中按时间平均的、按侵深平均的以及仅考虑准静态阶段的靶体阻力.模拟所得的各$R_{\rm t} $与用侵彻深度反向拟合的理论模型中的$R_{\rm t} $均表现出随速度增大而减小的趋势. 在速度超过2.5km/s后,前者变化缓慢, 而后者依然显著下降. 在4.5km/s的撞击速度下,由于侵彻深度超过流体动力学极限, 用侵彻深度反向拟合的$R_{\rm t}$为负值, 这显然与物理事实相违背.

由于Alekseevskii-Tate模型主要针对准静态阶段侵彻,因此用最终侵彻深度进行反向拟合求$R_{\rm t} $的方法不尽合理.Rosenberg和Dekel(1994b)采用零强度杆,仅模拟不发生弹体减速的定常侵彻, 所得$R_{\rm t}$随速度的变化程度更小, 在1$\sim $7km/s撞击速度范围内$R_{\rm t} $仅有20%变化. 因此他们认为靶体阻力与速度的相关性较小.国内学者楼建锋(2012)孔祥振等(2017)结合实验数据分析了Alekseevskii-Tate模型及其改进模型中靶体阻力项$R_{\rm t} $随侵彻速度和弹体速度的变化规律,发现Walker-Anderson模型更符合实验和模拟中靶体阻力变化情况. 此外,Lan-Wen模型中在一定的速度范围内能与Walker-Anderson模型反映出相同的靶体阻力随撞击速度下降的趋势.通过将Lan-Wen模型 (式(34), 令$C =1.5)$表达为类似Alekseevskii-Tate模型(式(13))的形式,可以得到$R_{\rm t} $的解析表达 (Lan & Wen 2010)

$$ R_{\rm t} = S + 2\rho _{\rm t} U_{\rm F0}^2 \exp\left[ { - \left( {\dfrac{u - U_{\rm F0} }{U_{\rm F0} }}\right)^2} \right] - \rho _{\rm t} uU_{\rm F0} \exp \left[ { -\left( {\dfrac{u - U_{\rm F0} }{U_{\rm F0} }} \right)^2} \right] (41)$$

联立$u$与$v$关系式即可得到靶体阻力$R_{\rm t} $与撞击速度$v$的关系.

实际上, Alekseevskii-Tate模型的控制方程式(13)可以表示为

$$ R_{\rm t} - Y_{\rm p} = \dfrac{1}{2}\rho _{\rm p}\left( {v - u} \right)^2 - \dfrac{1}{2}\rho _{\rm t} u^2 (42)$$

从上式可以看出, 在侵彻过程中$ R_{\rm t} - Y_{\rm p}$随速度变化而改变, Anderson等(1993)的模拟也反映了上述规律.Orphal和Anderson(2006)将侵彻速度与撞击速度的线性关系$u = a +bv$代入上式中, 得到了$R_{\rm t} - Y_{\rm p} $与撞击速度的显式关系

$$\left. {\begin{array}{l} R_{\rm t} - Y_{\rm p} = \left( {a^2 +2abV + b^2v^2} \right)\left( {\dfrac{1}{2}\rho _{\rm p} -\dfrac{1}{2}\rho _{\rm t} } \right) - a\rho _{\rm p} v - \left({b\rho _{\rm p} - \dfrac{1}{2}\rho _{\rm p} } \right)v^2 \\ \dfrac{\partial \left( {R_{\rm t} - Y_{\rm p} } \right)}{\partial v} = \dfrac{1}{2}\left({\rho _{\rm p} - \rho _{\rm t} } \right)\left( {2ab + 2b^2v}\right) - \rho _{\rm p} \left( {a + 2bv - v} \right) \\ \dfrac{\partial ^2\left( {R_{\rm t} - Y_{\rm p} } \right)}{\partial v^2} = \rho _{\rm p}\left( {b - 1} \right)^2 - \rho _{\rm t} b^2 \\ \end{array}} \right\} (43) $$

对于大多数材料, $a < 0$, $b > b_{\rm h} > 0$, $R_{\rm t} - Y_{\rm p}$随撞击速度先增大后减小. 在图13所示的两种弹靶材料组合中,$R_{\rm t} - Y_{\rm p}$均随撞击速度的增大呈现先增后减的规律. 图13中实线部分表示现有研究报道的结果,不同材料在现有研究的速度域内处在曲线的不同区域,这就解释了为何随撞击速度增大, $R_{\rm t} - Y_{\rm p}$在部分材料中增大 (Anderson & Walker et al.1992)而在另一些材料中减小 (Anderson et al. 1993).

图13   $R_{\rm t} - Y_{\rm p} $随撞击速度的变化曲线(Orphal & Anderson 2006)

   

在研究$R_{\rm t} $与速度关系时, 通常将$Y_{\rm p} $取为固定值(Anderson et al. 1992b, Anderson et al. 1993)或零强度 (Rosenberg & Dekel 1994b), 这样由式(43)可知金属靶体阻力$R_{\rm t}$在侵彻过程中随侵彻速度的增大而减小.

同时, 由于侵彻速度积分为侵彻深度, 故侵彻深度受$R_{\rm t}$的影响显著. Anderson和Walker(1991)发现在Alekseevskii-Tate模型中,无法同时匹配侵彻速度和侵彻深度. 笔者认为这正是由$R_{\rm t}$在侵彻过程中变化所导致的, 侵彻速度对应的是瞬时的$R_{\rm t} $,而侵彻深度应该对应积分平均化的$R_{\rm t} $.

需要特别说明, Anderson等(1993)指出靶板阻力$R_{\rm t}$随塑性区范围增大而增大, 而后者又与弹坑直径相联系.这也是Walker-Anderson模型和Lan-Wen模型等改进的半流体侵彻模型加入靶体响应区的原因.虽然Anderson等(1992b)认为塑性区范围在不可压时与速度无关,但若考虑可压缩性, 其范围将随速度的增大而减小. Anderson等(1993)在之后的分析中进一步认为在撞击速度大于1.5km/s时应该考虑可压缩性.然而 Song等(2018)指出, 在更高的速度下(大于4km/s)才能体现出可压缩性的影响,在长杆高速侵彻速度范围(1.5$\sim $3km/s)内可压缩性的影响极其微弱.

5.2 长杆高速侵彻中的弹体强度$Y_p $

5.2.1 弹体强度$Y_p $的物理意义与作用

通过对实验和模拟结果的分析, 研究者们(Hohler & Stilp 1987;Anderson et al. 1992b,1992a)普遍认为弹体强度对长杆高速侵彻能力的影响较小.因此在分析强度对侵彻能力的影响时, 通常取$Y_{\rm p}$为定值而研究$R_{\rm t} $的规律. 通过前文分析可知,采用侵彻深度反向拟合的$R_{\rm t} $不再是具有明确物理定义的参数.不同于其他研究者, Rosenberg和Dekel(1994b)认为由于$R_{\rm t}$与弹靶密度均无关, 且与速度的相关性也比较小, 故$R_{\rm t}$作为半流体理论模型中的强度项是合理的. Rosenberg和Dekel(2000)对不同强度长杆高速侵彻的模拟表明, $Y_{\rm p}$与弹靶强度、撞击速度和长径比都有关, 因而可以认为$Y_{\rm p}$是Alekseevskii-Tate模型中不能被明确定义的参数.

实际上, Anderson和Walker(1991)指出,影响弹体速度和侵彻速度进而影响侵彻深度的, 是模型中$R_{\rm t}$与$Y_{\rm p} $的差值$R_{\rm t} - Y_{\rm p} $, 而非两者本身.由于$Y_{\rm p} $控制弹体侵蚀和减速, Anderson和Walker(1991)建议通过实验测量弹尾的实时运动来推算$Y_{\rm p} $的值.

Rosenberg和Dekel(1998, 2012)指出, 弹体强度对侵彻能力有对立的两方面作用:一方面通过向靶板传递更高压力增加侵彻深度,另一方面导致弹尾减速从而降低侵彻深度. Rosenberg和Dekel(1994a)在对不同长径比弹体高速侵彻的模拟研究中发现, 长径比影响弹体强度作用,低强度的大长径比弹体的侵彻效率相较高强度弹更高,说明大长径比弹体中弹体减速作用较突出.

5.2.2 弹体强度$Y_p$与最大侵彻深度现象

通过对1.4$\sim $2.2km/s速度范围内钨合金撞击装甲钢靶的模拟,Rosenberg和Dekel(1996)发现侵彻深度-弹体强度曲线存在极值点,如图14所示. 该极值点与撞击速度的相关性较大,更高的撞击速度下达到最大侵彻深度所需的弹体强度更高.

图14   $L/D =10$长杆弹的无量纲侵彻深度--弹体强度曲线(Rosenberg & Dekel 1996)

   

该极值点现象结合前文所述的两种对立作用不难理解. 然而,现有的侵彻实验中弹体强度未能覆盖模拟中0$\sim$2.5GPa的强度分布, 故尚未观察到此现象. 再者, 由图14所示的Rosenberg和Dekel(1996)的模拟结果可看出,在更高的速度下侵彻深度--弹体强度曲线更加平缓,导致极值点更难观测到. 此外,诸如绝热剪切等其他因素将导致实际侵彻偏离半流体预测,也是此现象难以在实验中被观测到的原因.

值得注意的是, 上述现象与一维半流体侵彻模型所预测的$Y_{\rm p} >R_{\rm t} $的高强度杆弹会出现最大侵彻深度有本质差异.高强度杆的最大侵彻深度与侵彻后期的刚性侵彻有关, 在Rosenberg和Dekel(2000)的模拟中观测到明显的侵彻末端弹坑变窄 (刚性弹侵彻的标志),该现象在高达3km/s的速度下依然存在. 然而,自Alekseevskii-Tate模型提出几十年来,众多研究者的相关实验中只有Tate(1969)在铝杆侵彻铅靶的实验中观测到了高强度杆的最大侵彻深度.Rosenberg和Dekel(2000)整理相关实验结果并运用模拟手段分析了该现象,认为一维半流体侵彻模型所预测的$P/L$与$V$关系曲线上的极值点难以在现有的弹靶组合实验中被观测到.

此外, Rosenberg和Dekel(2000)还结合数值模拟结果讨论了长杆高速侵彻中超过流体动力学极限的部分与弹体强度的关系.根据Christman和Gehring(1966)给出的半经验侵彻深度公式 (式(2)),额外侵彻深度主要与密度比和剩余弹体动能相关. 然而Rosenberg和Dekel(2000)发现:(1)超过流体动力学极限的额外侵彻深度与弹靶强度比的相关性超过密度比;(2)弹体强度在高速下影响显著, 侵彻效率曲线斜率与弹体强度正相关;(3)额外侵彻深度与速度相关性小.

5.3 其他材料性质对长杆高速侵彻的影响 5.3.1 密度影响与侵彻结果的无量纲化

由早期实验数据分析可看出, 弹靶密度对侵彻深度影响显著.最直观的认识就是长杆高速侵彻的流体动力学极限即为弹靶密度比$1/\mu$. 然而Anderson等 (Anderson et al. 1992b, Anderson & Morris et al. 1992)总结实验数据发现,弹密度和靶密度对侵彻深度的贡献是不一样的,靶体密度与弹体密度相比对侵彻的影响较小, 如图15所示.

图15   $L /D = 10$长杆弹的无量纲侵彻深度--弹体强度曲线(Rosenberg & Dekel 1996)

   

目前大量的长杆高速侵彻数据通常表示为侵彻效率$P/L$与撞击速度$V$关系的形式, 不同弹靶组合之间难以横向对比.为理解侵彻过程的物理本质,需要对不同杆/靶组合的侵彻结果进行无量纲化,以得到确定的相似关系并大幅减少工作量.

通过引入弹尾临界速度$V_{\rm c} = \sqrt {{2\left| {R_{\rm t} -Y_{\rm p} } \right|} / {\rho _{\rm p} }} $, Rosenberg和Dekel(2001)发现侵彻仅存在强度差别的不同靶的模拟结果均分布在$P/L$与$V /{V_{\rm c} }$的单一曲线上,对钨合金杆撞击不同硬度钢靶的实验结果的无量纲化也得到了相同的结果(如图16(a)所示). 再者, 通过引入弹靶密度比$\mu = \sqrt {{\rho_{\rm t} } /{\rho _{\rm p} }} $,具有不同密度比的杆/靶组合的相似关系可以清晰地展现出来. 因此,Rosenberg和Dekel(2001)分别运用$V_{\rm c} $和$\mu L$来对撞击速度$V$和侵彻深度$P$进行无量纲化的方法是值得推荐的.

图16   侵彻结果的无量纲化方法 (Rosenberg & Dekel 2001). (a)钨合金杆撞击不同硬度钢靶实验结果的无量纲化,(b)不同弹靶组合的两组侵彻数据的无量纲化

   

Rosenberg和Dekel(2001)发现, 钨杆(金杆)侵彻钢靶和钢杆侵彻铝靶的侵彻数据有很高的相似性 (如图16(b)所示), 两者的弹靶密度比分别为1.5$\sim $1.6和1.7. 此外,具有相似密度比的钛合金杆侵彻铝靶 $(\mu = 1.66 )$和铝杆侵彻镁靶$(\mu = 1.64 )$的实验结果也有很高的相似性. Orphal(2006)采用上述无量纲方法,发现SiC、AlN和B$_{4}$C3种陶瓷的侵彻实验结果近乎分布于同一曲线上.从以上对实验和模拟结果的无量纲分析可以看出,具有相似密度比的弹靶组合容易出现侵彻结果的相似性.

具有相似关系的侵彻结果一方面可以反映类似的侵彻机理,另一方面也可用于弹靶组合的选材和设计. Orphal和Franzen(1990)的实验已采用密度比相近的铜撞铝来替代钨撞钢,以后更多实验也可考虑利用相似关系把难制备或成本高的材料替换为简单廉价的材料.

5.3.2 弹/靶材料热软化、绝热剪切与失效应变

(1) 弹/靶材料的热软化

Rosenberg和Dekel(1998)发现, 在弹体材料本构关系中增加热软化机制, 则图14所示的侵彻深度--弹体强度曲线的极值现象消失, 如图17所示. 然而,单独考虑靶体的热软化不会使极值现象消失. 此外,考虑弹和靶的热软化均会提高侵彻深度, 该现象在高强度杆侵彻中尤为突出.

图17   热软化对钨合金侵彻钢靶的影响 (Rosenberg & Dekel 2004)

   

在数值模拟中通常用Johnson-Cook本构 (Johnson & Cook 1983)或Steinberg本构 (Steinberg 1987)考虑热软化,或是将最大失效应变$\varepsilon _{\rm f} $引入von Mises屈服准则.Rosenberg和Dekel(2004)总结了前人在数值模拟中采用的本构模型和屈服准则并对其效果进行了分析.

此外还需指出的是, 软化对于陶瓷材料抗侵彻的数值模拟更加重要.由于陶瓷靶中侵彻机理比金属靶更复杂, 本文将在后文对此进行讨论.

(2) 弹体材料的绝热剪切与失效应变

Magness和Farand(1990)发现密度与强度几乎一样的贫铀(DU)杆与钨合金 (WHA)杆侵彻装甲钢靶 (RHA)时,前者的侵彻效率高很多. 如图18所示, 在1.2$\sim $ 1.9km/s速度范围内,两种杆材的实验数据点在无量纲侵彻深度--速度曲线上分布于两条明显分开且近乎平行的直线上;更高的撞击速度(大于2.0km/s) 下两组数据趋近于同一曲线.Magness和Farand(1990)将上述现象归功于贫铀材料的绝热剪切失效倾向导致的“自锐”特性.由于贫铀材料在相对较低的应变下因绝热剪切失效,故贫铀杆弹的头部比钨合金杆弹更尖锐.

图18   DU和WHA杆侵彻RHA的实验数据 (Magness & Frarand 1990)

   

图18可以看出, 撞击速度约为2.0km/s时,贫铀与钨合金杆的侵彻能力几乎相同.为解释绝热剪切效应在高速下趋于消失的问题, Rosenberg和Dekel(1998)在杆弹材料本构关系中加入失效应变$\varepsilon _{\rm f}$进行数值模拟. 如图19所示, $L/D =20$的钨合金杆以不同速度撞击RHA, 钨合金材料的$\varepsilon _{\rm f}$在0到5.0的范围内引起侵彻深度的显著变化. 由于$\varepsilon _{\rm f}$对侵彻深度的影响与撞击速度强烈相关, 随撞击速度的提高,影响程度下降明显, 故图18中绝热剪切效应的消失现象可由图19中2.1km/s速度下的平缓曲线予以解释.

图19   失效应变对无量纲侵彻深度影响 (Rosenberg & Dekel 1998)

   

Rosenberg和Dekel(2004)指出, 在对长杆高速侵彻的模拟中,假设应变超过失效阈值后杆弹头部单元失去强度,可以更简单地描述侵彻过程中的材料软化效应. 此外, 通过引入失效应变,Rosenberg和Dekel(2003)还模拟出了刚性弹向半流体侵彻转变时侵彻深度下降的典型现象.

Anderson等(1999)假设单位体积的弹体材料在失效前能吸收的塑性功为常数,建立了材料强度$Y_{\rm p} $与失效应变$\varepsilon _{\rm f}$之间的关系,该关系和强度较高的钢材在拉伸试验中延伸率较低的实验结果一致. 此外,Anderson等(1999)还建议$\varepsilon _{\rm f}$应与材料在动态加载下所能承受的最大应变相关联.

6 长杆弹头部形状对侵彻能力的影响

众所周知, 弹体头部形状对刚性弹侵彻能力有显著影响.相当多研究工作已对此展开了详细讨论: Forrestal等(1994,1996)基于空腔膨胀理论提出了分析尖卵头弹体侵彻阻力的经验公式,Chen和Li (Chen & Li 2002, Li & Chen 2003)引入形状因子$N^\ast $分析了不同头形刚性弹的侵彻能力, Zhao等(2010)建立了形状因子$N^\ast $和撞击速度的关系, Liu等(2015)对双尖卵头弹体的形状因子与侵彻阻力进行了分析.相较于刚性弹侵彻, 弹体头部形状对长杆侵彻的影响的研究报道较少.虽然一部分研究者认为更高速度下弹体发生侵蚀将导致头部形状因素不再重要,然而Magness和Farand(1990)的实验却发现,密度与强度几乎一样的贫铀杆与钨合金杆在1.2$\sim $1.9km/s速度范围内对装甲钢靶的侵彻效率相差达10% (如图18所示).因此, 长杆侵彻中弹体头部形状影响不可忽视.

由于长杆侵彻中弹体发生侵蚀, 侵彻过程中头部形状与初始弹头形状可能存在差异,故相应研究工作应分别考虑初始弹头形状和侵彻过程中弹头形状的影响.

6.1 初始弹头形状对长杆侵彻能力的影响

Walker和Anderson(1994)采用CTH程序对钝头、半球头和锥头的钨合金长杆弹侵彻4340钢靶进行模拟,研究了初始弹头形状对侵彻能力影响. 图20展示了不同初

图20   不同头形弹体在侵彻过程中的头形、压力分布和速度分布变化(Walker & Anderson 1994)

   

始头形弹体在侵彻过程中头形变化过程以及压力和速度分布.模拟结果表明, 初始弹头形状对侵彻影响仅存在于侵彻最初阶段,不同头形杆弹在侵彻约两倍杆径后侵彻速度与弹头形状均保持一致.初始弹头影响侵彻初期的界面压力大小进而导致弹体破坏程度和靶体塑性区大小的差异,并造成侵彻速度不同.锥头、半球头和钝头弹体的塑性区大小与侵彻速度依次增加.

Rosenberg和Dekel(1999)通过模拟比较了5种不同头形长杆弹的侵彻能力的差异,模拟结果如图21所示, 不同头形弹体的最终侵彻深度差异较大.程兴旺等(2007)的数值模拟结果与上述结果相反,弹头形状仅影响弹坑形貌而对侵彻能力影响较小.两个模拟工作最大区别在于弹体材料本构,后者采用的是长杆侵彻中最常用的Johnson-Cook本构,而前者为了避免Walker和Anderson(1994)所提到的侵彻初期后弹头形状趋于一致选择了理想弹性本构. 因此,Rosenberg和Dekel(1999)的模拟实际上反映的是侵彻过程中弹体头部形状的影响.现有的一维理论分析模型显然无法反映上述特征,故需要建立考虑弹头形状的2D理论分析模型.

图21   5种不同头形弹体的最终侵彻深度 (Rosenberg & Dekel 1999)

   

此外,初始弹头形状对长杆侵彻能力的影响还受到弹靶强度与撞击速度的制约.高光发等(2012)通过数值模拟认为: 在较低的撞击速度下存在最佳头形,而在较高的速度下初始头形仅对开坑阶段有影响, 故初始头形影响较小;在侵彻低强度的脆性靶 (如混凝土靶)时,不同初始头形弹体出现头部扩大的阈值速度不同,对应的侵彻能力差异也十分显著.

初始头形影响还体现在界面击溃中. Lundberg等(2006)开展的长杆弹对陶瓷靶的界面击溃实验分析了初始弹头形状的影响,谈梦婷等(2016)对不同初始头形长杆的界面击溃开展了数值模拟, Li等(2014,2017)通过建立界面击溃和斜击溃的2D理论模型进一步分析了初始弹头形状的影响.相关研究结果将在后文中加以讨论.

综上,弹体初始头形将影响初始瞬态阶段界面压力大小并导致弹体破坏程度和靶体塑性区大小的差异,进而影响侵彻性能.由于初始头形影响主要体现在长杆高速侵彻的初始瞬态阶段,故开坑直径受影响较大而侵彻深度受影响较小. 然而,若计及头形在侵彻过程中演化, 初始头形对侵彻能力影响将增大. 因此,结合实验、模拟和理论手段,深入分析初始弹头形状在侵彻过程中的演化规律, 将是下一步工作的重点.

6.2 侵彻过程中弹头形状对长杆侵彻能力的影响

从前文分析可知,侵彻过程中的不同弹体头形实际上是由材料性质的差异所导致.长杆高速侵彻实验中, 使用较多的弹体材料为钨合金、铝和钢 (Anderson & Morris et al. 1992),实验观测到的侵彻过程中弹体头部形状多为蘑菇头形. Magness和Farrand(1990)的实验中,贫铀杆弹在侵彻过程中具有比钨合金杆弹更尖锐的头部形状.因此,贫铀杆与钨合金杆侵彻能力差异的本质,是两者的材料性质差异导致侵彻过程中出现不同的弹体头部形状.

Rosenberg和Dekel(1999)针对钨合金/RHA、钛合金/铝、铜/铝合金3组弹靶组合开展了长杆侵彻(贯穿)有限厚靶的实验,进一步验证了材料性质差异导致长杆弹在侵彻过程中的不同头形.3组弹靶组合的弹靶 密度比相近,而Ti/6Al/4V钛合金材料具有与贫铀材料相似的绝热剪切性质.实验采用闪光X射线摄影拍摄到的侵彻过程中弹头形状与和后置沙盒减速后回收的剩余弹体头部形状如图22所示. 两者均反映出侵彻过程中的弹头形状与弹体材料性质相关:铜所代表的完全延性材料呈现出蘑菇头,钨合金所代表的半脆性材料表现为部分蘑菇头,而以Ti/6Al/4V钛合金为代表的绝热剪切材料则出现凿形尖头.

图22   长杆侵彻(贯穿)有限厚靶实验中闪光X射线照片和回收的剩余弹体形貌 (Rosenberg & Dekel 1999)

   

Magness和Farrand(1990)的实验说明, 贫铀杆弹由于绝热剪切性质,在侵彻过程中保持尖锐的头部形状. Rosenberg和Dekel(1999)的实验则表明,Ti/6Al/4V钛合金材料由于具有与贫铀材料相似的绝热剪切性质,杆弹在侵彻过程中同样具有尖锐头形. Rong等(2012)和陈小伟等 (陈小伟等 2012,Chen et al. 2015)的实验还发现, 纤维增强金属玻璃等其他材料亦具有“自锐”效应(李继承和陈小伟 2011). Li等(2015a)的数值模拟和理论分析表明,这种“自锐”效应将导致弹体所受阻力降低, 从而具有比WHA更好的侵彻能力. 此外,Li等(2015a)还指出,撞击速度、靶体强度和初始头形将影响“自锐”效应进而影响长杆弹侵彻能力.上述研究证明了材料性质差异导致的侵彻过程中的不同头形对长杆高速侵彻性能的影响,然而对于由此带来的侵彻机理的改变仍缺乏深入研究.

实际上,弹体头形对长杆高速侵彻能力的影响与最终弹坑直径有很大的关系.不同于刚性弹侵彻, 长杆高速侵彻的弹坑直径可达数倍于弹体直径,同时弹坑直径在高速下的增长率远超过侵彻深度的增长率.从能量耗散的角度定性分析, 在较高的撞击速度下,弹孔横向扩张消耗部分能量, 削弱了弹体的轴向侵彻能力 (Rosenberg & Dekel 2012). 对于弹体在侵彻过程中的不同头形,横向扩孔所消耗的能量存在差异, 进而导致侵彻能力的不同.

通过拟合实验数据, Bierke等(1992)Walker等(2001)得到了长杆高速侵彻弹坑直径的经验公式 (式(4)和式(5)). 然而,上述经验公式由于缺乏物理依据,弹坑直径仅与杆弹直径和初始撞击速度有关而不包含弹靶材料参数,故仅适用于特定弹靶组合. 基于能量守恒, Tate(1986)建立了开坑的近似模型. Lee和Bless(1996)根据动量守恒从理论上推导出了弹坑直径$D_{\rm c} $的表达式

$$ D_{\rm c} = D_{\rm p} \sqrt {\dfrac{Y_{\rm p}}{R_{\rm t} } + \dfrac{2\rho _{\rm p} \left( {V - U}\right)^2}{R_{\rm t} }} (44) $$

在此基础上, Lee和Bless(1998)提出了两阶段式开坑模型,将侵彻过程分为蘑菇头阶段和空化阶段 (靶体惯性运动); Wen等(2010)建立横向开坑计算模型, 预测了弹体蘑菇头半径. 然而,上述研究侧重于计算和预测最终开坑直径,缺乏从能量耗散的角度分析横向开坑对于纵向侵彻能力的影响. 此外,模型中对侵彻过程中弹体头部为半球面蘑菇头的假设缺乏一般性.

为进一步研究侵彻过程中头形对长杆侵彻的影响,分析侵彻过程中弹体头形对弹坑形貌的影响以及弹坑横向尺寸与纵向尺寸(侵彻深度)之间的联系, 需开展更多实验和模拟工作,特别是针对长杆侵彻中占比最高的准定常阶段进行分析. 同时,由于现有的一维理论分析模型无法反映弹头形状的影响,需要建立考虑弹头形状的2D理论分析模型, 对弹坑直径和侵彻深度做出更准确的预测.

7 长径比效应与分段杆设计

7.1 长径比效应及其作用机理

长径比效应是长杆侵彻中一个重要的现象, Tate等(1978)用$L/D$分别为3, 6和12的钨合金杆撞击装甲钢靶, 发现随着长径比的增大,侵彻效率下降明显. 随后, Hohler和Stilp(1987)整理大量实验数据发现,大长径比杆弹的侵彻效率$P / L$低于短杆的侵彻效率,并称此现象为长径比效应.

7.1.1 长径比效应的作用范围与影响程度

Tate等(1978)以及后来的很多研究者都认为, 该趋势在$L /D =10$时即饱和, 即所有$L /D \geq 10$的数据点将会落在同一条$P /L-V$的曲线上. 然而, Hohler和Stilp(1987)的实验数据显示, $L /D$为20和30的长杆的侵彻效率仍有显著降低, 在1.5km/s的撞击速度下$L/ D$为30的长杆的侵彻效率仅为$L/D = 10$的长杆的50%.Rosenberg和Dekel(1994a)以及Anderson(2003)等重做了上述实验并整理了其他实验来源后, 均认为Hohler和Stilp(1987)的结果对于长径比对侵彻深度的影响程度有过高估计. 实际上,在兵器速度范围内, $L/D$为10和20的长杆侵彻效率之间的差距仅有15%, $L/D = 10$与$L /D =30$的长杆相差也不过30%.

Rosenberg和Dekel(1994a)对不同强度、不同长径比的钨合金长杆以1.4km/s的速度撞击装甲钢靶的数值模拟重现长径比效应,模拟结果如图23所示. 模拟表明:(1)不同强度的弹体对长径比有不同的敏感度;(2)即使是零强度的杆弹也具有长径比效应;(3)在长径比高达40时长径比效应依然存在.

图23   不同强度长杆的无量纲侵彻深度随长径比的变化情况(Rosenberg & Dekel 1994a)

   

Anderson等(1996)模拟分析了1.5km/s撞击速度下长径比从1到30的杆弹侵彻能力.图24中实心菱形表示模拟结果,空心圆、方块和菱形分别反映不同来源的的实验数据点.模拟结果能反映实验数据变化趋势, 通过对上述数据的最小二乘拟合,Anderson等(1996)得到了经验公式 (式(3)). 图24实线即为式(3)所算结果, 该经验公式能概括兵器速度范围内 $(0.8\leq \bar {V} \leq 1.8)$钨合金杆侵彻装甲钢靶的结果.式中第三项系数为负, 侵彻效率$P /L$随长径比$L / D$增大而减小. 此外,从图24还可看出, 1.2,1.5和1.8km/s撞击速度下无量纲侵彻深度变化趋势一致, 故Anderson等(1995)认为兵器速度范围内长径比效应与速度无关.

图24   不同速度下无量纲侵彻深度与长径比的关系 (Anderson et al. 1995)

   

7.1.2 长径比效应的无量纲分析

Anderson等(1996)采用$P/D-{L_{\rm e} }/ D$的形式对长径比为3$\sim$30的钨合金杆撞击装甲钢靶的模拟结果进行无量纲分析, 其中${L_{\rm e} } / D$表示用弹体直径无量纲化的弹体侵蚀部分长度. 如图25所示, 除了短杆在侵彻末端的偏差, 在1.5km/s撞击速度下不同长径比的侵彻数据都能重合于一条曲线上.图中箭头指向不同杆弹的侵彻终点 (即最终侵彻深度),而曲线斜率即表示侵彻效率$P / L$. 曲线向下弯曲,说明侵蚀单位长度弹体对应的侵彻深度减少, 因此侵彻效率下降.

图25   无量纲侵彻深度与无量纲弹体侵蚀长度的关系 (Anderson et al. 1996)

   

7.1.3 长径比效应的作用机理

上述实验和模拟证实了长径比对侵彻效率的影响及其程度,然而其作用机理更值得研究. 根据已有研究结论,长径比效应的原因主要可以归纳为弹体减速、瞬态阶段和次级侵彻3个部分.此外Anderson等(1996)还建议靶体内塑性区的增长对长径比效应有贡献.

(1) 弹体减速

Anderson等(1996)通过分析长径比对侵彻速度的影响,发现弹体减速是兵器速度范围内出现长径比效应的主要原因.由于弹体减速正比于弹体强度, Rosenberg和Dekel(1994a)模拟结果中有强度杆比零强度杆具有更显著的长径比效应 (如图23)恰能说明弹体减速的作用. 需特别说明的是,弹体减速和次级侵彻是耦合作用的. 通常认为主要侵彻阶段准定常,弹体减速较小. 因此, 弹体减速作用主要体现在次级侵彻阶段.

(2) 瞬态阶段

零强度的杆弹依然存在长径比效应, 说明弹体减速并非唯一因素.Rosenberg和Dekel(1994a)认为初始瞬态阶段较低的侵彻阻力导致侵彻深度增加进而导致长径比效应.Anderon和Orphal(2008)的模拟说明, 主要(准定常)侵彻阶段在侵彻深度达到数倍杆径后才成立. 因此,通过确定初始开坑阶段的占比可以定性估计长径比效应的程度.Rosenberg和Dekel(2012)指出,长杆高速侵彻的侵彻深度约为杆弹初始长度的1.0$\sim $1.5倍, 即$L/D = 10$长杆的侵彻深度为$\left( {10\sim 15} \right)D$.由于开坑阶段大概持续5倍杆径范围, 这意味着$L /D =10$长杆的准定常侵彻阶段仅占总侵彻深度的1/2, 故$L/D$在10$\sim$30范围内长径比效应的影响不难理解.

(3) 次级侵彻

Anderson等(1995)分析长径比效应与撞击速度的关系,发现不同速度下作用机理有差异: 兵器速度范围内, 弹体减速是主要原因;更高速度下长径比效应则归因于次级侵彻. 图26展示了5组不同撞击速度下不同长径比弹体的侵彻能力,不同速度下长径比效应存在不同特征: 较低速度下 (1.5km/s),长径比效应主要作用于准定常阶段, 弹体减速导致侵彻能力下降,在图中表现为曲线向下弯曲; 然而对于更高的侵彻速度 $(>2.0$km/s),准定常阶段表现为一条直线, 故该阶段内并无长径比效应,而图中侵彻末端曲线往上弯曲,说明更高速度下长径比效应归功于次级侵彻阶段.

图26   不同速度下无量纲侵彻深度与无量纲弹体侵蚀长度的关系(Anderson et al. 1995)

   

次级侵彻阶段的侵彻深度实际上与长径比无关, 而与侵彻速度相关.侵彻深度可用以下经验公式概括

$$ P = T\left[ {V,\rho _{\rm p} ,\rho _{\rm t} ,Y_{\rm t},Y_{\rm p} } \right] \cdot \left( {L - D} \right) + \mu V^{2 /3}D (45) $$

其中, $T\left[ {V,\rho _{\rm p} ,\rho _{\rm t},Y_{\rm t} ,Y_{\rm p} } \right]$是主要侵彻阶段无量纲侵彻深度,由半流体侵彻理论计算所得. 次级侵彻深度与速度的2/3次方成正比, 因此,较高速度下长径比效应随撞击速度的增大而增大.

综上, 长径比效应主要由弹体减速、瞬态阶段和次级侵彻导致. 因此,为获得更高侵彻效率, 需降低杆材强度以减弱弹体减速,或改变结构以缩短侵彻阶段作用时间.

7.2 长径比效应的应用: 分段杆

根据长径比效应, 细长杆的侵彻效率不如短粗杆,但相同质量下细长杆由于初始弹体长度更长仍具有更强侵彻能力.针对以上特征,将连续长杆切分为相隔一定距离的几段杆弹成为一种新的弹体构型思路.

由前文分析, 小长径比分段子杆主要侵彻阶段作用时间短,弹体主要处于初始瞬态阶段和次级侵彻阶段, 因而具有很高的侵彻效率.同时由于分段杆与连续杆具有相同的有效长度,故其侵彻能力比连续杆更强. 此外, 根据理论预测,长杆弹的侵彻效率随速度的增加最终趋于流体动力学极限而饱和, 而$L/D =1$的短杆和球形弹丸的侵彻深度正比于$v^{2/3}$因而在高速下亦不会饱和. 因此, 从理论上说,采用数段短杆间隔发射将大幅提高侵彻能力,侵彻能力的提升在高速下更加明显.

Orphal于1982年率先开展的分段杆撞击小混凝土块的实验证实了上述结论(Orphal 2006). Hohler和Stilp(1987)总结了20世纪80年代的在分段杆方面为数不多的几个工作, 认为在2km/s以上的速度下分段杆的侵彻能力优于连续长杆.随着实验技术的发展和模拟计算的完善,针对分段杆的大量研究工作出现于90年代. 其中,一部分实验采用逆向弹道的方法进行, 诸如Orphal和Franzen(1990)、Orphal和Miller(1991)和Westerling等(1997);另一部分则采用大尺寸正向弹道实验, 以Charters等(1990)、Cuadros(1990)、Sorensen等(1991)及Wang等(1995)为代表.由于分段杆实验复杂且昂贵, 目前多采用数值模拟作为主要研究手段,以Sorensen等(1991)、Wang等(1995)、郎林等(2011)以及Aly和Li(2008)的工作为代表.

7.2.1 分段杆的典型实验

运用小尺寸逆向弹道技术, Orphal和Franzen(1990)开展了分段球形铜弹丸撞击铝靶的实验.实验采用7075-T6铝靶以3.3km/s向间隔$2.4D$放置的直径为$D =1.59{\rm mm}$的8颗球形铜弹丸,弹靶材料组合的选取考虑到铜/铝与钨/钢的密度比相近.实验中顺次拍摄到的4幅X光片如图27所示, 由图27可看出,该间距下各段几乎独立起作用, 靶中弹孔足够大而不影响后面的分段子杆.

图27   8颗球形铜弹丸侵彻铝靶实验的X光片 (Orphal & Franzen 1990)

   

Orphal和Franzen(1990)还结合模拟结果考察了4.5km/s撞击速度下段间距对分段铜弹丸与铝靶组合侵彻性能的影响, ${L_i }/ D = 1$分段子杆的最佳间距在2.4到3.6倍弹体直径之间. 随间距增大,侵彻效率$P /{\sum L_i }$ $(\sum L_i $为分段子杆长度的总和,即有效杆长)接近1.6, 而对应的$L /D = 8$连续杆侵彻效率$P/L$约为1.05, 分段杆侵彻效率比连续杆高60%.

Charters等(1990)采用大尺寸正向弹道实验,研究了连续长杆和不同段间距分段杆的侵彻性能,实验设计与结果展示于图28中. 从图中可以看出, 2.5km/s速度下段间距从$1D$增加到$2D$, 分段杆较侵彻能力提高约20%.结合一系列实验结果, Charters等(1990)发现分段杆和连续杆侵彻能力的优劣取决于比较标准:同质量同直径下分段杆侵彻能力更强, 而同质量同总长(大于有效杆长)下连续杆侵彻能力更强.

图28   连续与分段钨杆侵彻钢靶的弹坑X光片 (Charters et al. 1990)

   

虽然以上两组实验分别采用不同的发射技术, 但实验结果接近,因而可信度高. 小尺寸逆向弹道实验由于需要判断剩余分段子杆数目,故不可避免地存在15%左右的误差 (Orphal & Miller 1991);而大尺寸正向弹道实验可以通过回收靶板直接测量侵彻深度,不存在上述测量误差.

其他实验结果之间的差异可能是因为段间填充材料以及连接分段子杆的套筒对侵彻效果的影响.Orphal和Franzen(1990)研究的理想分段杆间无填充和连接, 而Charters等(1990)在分段杆间有不同材料制成的串联链杆, Cuadros(1990)Sorensen等(1991)则采用了更复杂的管状套筒加段间填充物的结构.

7.2.2 连接结构对分段杆侵彻性能的影响

在实际应用中, 为保证结构的完整性和稳定性,需要在分段子杆外加装套筒或在子杆间加入填充材料. 因此,分析连接结构对分段杆侵彻能力的影响对分段杆武器设计具有重要意义.

Charters等(1990)认为不同连接结构对侵彻有不同作用效果:分段杆间轴线连接会增强侵彻能力,而套筒加填充物式支撑结构则会削弱侵彻能力. Orphal和Miller(1991)研究了带套筒及含填充物 (轴线连接)的各种非理想分段杆结构,认为它们对侵彻性能影响不大.

Sorensen等(1991)的实验和模拟都表明,玻璃纤维填充材料对侵彻能力有显著增强作用,一方面是由于增加了弹体的整体质量, 另一方面则是因为次级侵彻. 同时,他们在模拟中发现,无填充分段杆的套筒材料在侵彻时流入分段杆与靶体的中间区域, 如图29所示,这将导致部分分段杆在侵彻过程中实际上是在侵彻铝套筒材料而非靶体材料,从而降低侵彻能力.

图29   带有铝套筒的钨合金分段杆侵彻RHA的数值模拟 (Sorensen et al. 1991)

   

郎林等(2011)通过数值模拟发现, 加入套筒虽然大幅提高了整体结构动能,但侵彻深度仅略微增大, 套筒的贡献主要在于扩张弹坑直径. 需说明的是,郎林等(2011)研究的撞击速度属于低速 (2.0km/s), 而Wang等(1995)在该速度范围内实验发现存在转变速度,在此速度之上同质量同直径的分段杆侵彻能力明显高于连续杆.

Aly和Li(2008)对更宽的速度范围内的非理想分段杆(含套筒和填充物)进行了数值模拟,综合分析了套筒与填充物对分段杆侵彻能力的作用.通过分析能量传递和弹坑形貌他们发现, 在1.8$\sim$2.0km/s的速度范围内, 套筒和填充物上的动能主要用于弹孔的扩大,与理想分段杆的圆齿状弹孔相比, 非理想分段杆的弹孔更光滑. 此外,模拟中还观测到了套筒材料向内流动 (同Sorensen等(1991))和向外流动两种现象, 如图30所示. 在低速下,向内流动的套筒材料将导致侵彻能力下降,而填充物能阻碍套筒材料的向内流动;高速下套筒与填充物均对弹坑的深度和直径有贡献.

图30   4.2km/s撞击速度下含套筒分段杆的侵彻图像 (Aly & Li 2008). (a)套筒材料向内流动, (b) 和向外流动

   

7.2.3 段间距的影响与$L /D < 1$的短杆侵彻

Orphal和Franzen(1990)Hohler和Stilp(2002)都发现,虽然增大段间距能提高侵彻能力, 但一定速度下存在一个段间距的最佳值,超过此值后继续增大段间距对提高侵彻能力无益. Sorensen等(1991)发现段间距对侵彻能力的影响与分段子杆长径比有关,段间距对${L_i } /D = 1$分段杆的影响小于${L_i }/D = 1.5$分段杆.

笔者认为, 上述现象可以解释为最佳段间距需保证各分段子杆独立作用,满足${L_i }/D = 1$的分段子杆独立作用所需的段间距相较${L_i }/D =1.5$更短, 因而最佳段间距更小, 故段间距的影响更小. 据此推测,低速下段间距的影响也应更小. Wang等(1995)发现, 在1.9$\sim $2.1km/s的撞击速度下${L_i } /D = 1$分段杆的段间距从0.5$D$增加至1$D$,侵彻深度仅提高了2%$\sim $5%, 符合上述推测.

Orphal和Franzen(1990)发现${L_i }/ D = 1$分段杆侵彻深度正比于$v^{2/3}$, 而${L_i } / D < 1$分段杆侵彻深度随速度增幅大于$v^{2/3}$,因此他们建议将连续长杆分成更多${L_i }/D < 1$分段杆以提高侵彻能力.Franzen等(1994)发现, 不同撞击速度下存在不同最佳长径比. Walker(1999)建立$L/D < 1$短杆侵彻理论模型, 较好地解释了相关实验数据.

8 陶瓷靶抵抗长杆侵彻与界面击溃

陶瓷材料具有高强度和低密度的特点, 被广泛应用于防护装甲设计.近几十年来, 国内外学者对陶瓷靶装甲各方面特性已展开广泛研究,本文重点关注陶瓷靶在抵抗长杆侵彻以及界面击溃方面的研究工作.

8.1 陶瓷靶抵抗长杆侵彻

陈小伟和陈裕泽(2006)已对陶瓷靶高速侵彻/穿甲动力学的研究进行了较全面的综述,重点关注了单质陶瓷靶和陶瓷复合靶的侵彻机理、空腔膨胀模型的应用和失效波效应.本节侧重介绍陶瓷靶抵抗长杆侵彻的防护效率和靶体阻力:前者关注防护效率值的范围和影响因素,对于装甲设计工程师有重要的指导意义;对后者的分析能体现出陶瓷靶靶体阻力与金属靶的差异.

8.1.1 陶瓷靶抵抗长杆侵彻的防护效率

Yaziv等(1986)将陶瓷靶抵抗长杆侵彻的弹道防护效率定义为:抵抗给定威胁时所需的面密度 (防护结构材料密度乘以厚度,单位为kg/m$^2)$与参考靶板需要的面密度之比.为消除背面厚度对防护效率的影响, 厚度$h_{\rm c} $、密度$\rho _{\rm c} $的陶瓷板粘贴在作为参考材料的厚金属块上 (如图5所示),通过弹体对厚衬板的剩余侵彻深度来反映陶瓷材料的防护效率.以铝作参考材料为例, 陶瓷靶的防护效率可表示为

$$\eta = \dfrac{\rho _{\rm Al} \left( {P_{\rm Al} -P_{\rm res} } \right)}{\rho _{\rm c} h_{\rm c} } (46) $$

式中, $P_{\rm res} $和$P_{\rm Al}$分别为弹体对厚衬板的剩余侵彻深度和对无陶瓷覆盖铝块的侵彻深度.上式可继续外推至剩余侵彻深度$P_{\rm res} = 0$, 即

$$ \eta = \dfrac{\rho _{\rm Al} P_{\rm Al} }{\rho _{\rm c} h_{\rm c}^\ast } (47) $$

式中, $h_{\rm c}^\ast$为剩余侵彻深度为零所需的最小陶瓷厚度. 上式说明,若实验结果用面密度表示,则防护效率即为通过实验数据点的拟合直线斜率.

最早由Bless等(1987)报道的陶瓷材料抵抗长杆侵彻的DOP实验将氧化铝陶瓷粘贴在厚铝衬块上,Mellgard等(1989)建议采用装甲钢作为衬板材料以降低杆的剩余侵彻深度,Hauver等(1992)将陶瓷板嵌于钢衬板内以提供更好的约束条件同时削弱横向稀疏波效应.

Hohler等(1995)分析了以硬钢为背衬的厚度为10$\sim$80mm的氧化铝陶瓷抵抗$L/D = 12$钨合金杆侵彻的实验,实验结果如图31所示. Rosenberg等(1997)整理上述实验数据,发现在1.25km/s,1.7km/s和3.0km/s的撞击速度下剩余侵彻深度--陶瓷厚度数据分布于近乎平行的3条直线上,证明陶瓷材料抵抗长杆侵彻的效率与撞击速度无关. 然而, Madhu等(2005)对穿甲弹以0.5$\sim$0.83km/s的速度侵彻氧化铝陶瓷靶的实验则表现出弹道防护效率与速度的相关性.Zhang等(2011)通过数值模拟复现了Madhu等(2005)的实验,并认为在低于1.3km/s的速度下陶瓷的防护效率随速度提高而增大,高于1.3km/s后弹道防护效率无明显差异.

图31   $L /D = 12$的钨合金杆以不同速度撞击氧化铝陶瓷 /钢衬靶的DOP实验结果(Hohler et al. 1995)

   

值得注意的是, Hohler等(1995)实验得到的氧化铝陶瓷抵抗长杆侵彻的防护效率$\eta =1.7$略低于典型值$\eta = 2.0$,这是由于实验所用的钢衬块强度比普通RHA更高. 因此,陶瓷的防护效率与背衬材料相关, 对于特定的陶瓷材料,提高背衬材料强度会降低防护效率值. Rosenberg等(1998)开展了以高硬度钢为背衬的不同陶瓷材料的DOP实验, 实验采用$L/D= 12.5$的钨合金杆以1.7km/s撞击靶体,得到的剩余侵彻深度--陶瓷面密度曲线如图32所示.不同陶瓷材料的实验数据分布于两条直线之间,高强陶瓷相对高硬度钢衬的典型防护效率值$\eta $为1.7$\sim $2.7. Reaugh等(1999)采用$L /D =4$的钨合金短杆以同样速度撞击高强度钢为衬板的不同陶瓷靶得到了类似结果,不同材料的防护效率值为2.0$\sim $3.1. 从图32还能看出,横向尺寸小的陶瓷板的防护效率值$\eta $更低,这是由于横向稀疏波衰减了长杆/陶瓷界面附近的高压.为了提高陶瓷防护效率, 一方面需要避免上述横向边界影响,采用更大的陶瓷板或将陶瓷板嵌于衬板内;另一方面还需注意靶体内部陶瓷板与衬板的声阻匹配. 此外,使用盖板等约束和提供合适的预应力也可提升陶瓷的防护性能.

图32   不同陶瓷的DOP实验结果 (Rosenberg et al. 1998)

   

8.1.2 陶瓷靶抵抗长杆侵彻的靶体阻力$R_t$

在陶瓷靶抵抗长杆侵彻的理论分析中, 最常用的是Alekseevskii-Tate模型.Rosenberg和Tsaliah(1990)发现陶瓷与金属一样存在开始侵彻的阈值速度$V_{\rm c} $,进而论证了Alekseevskii-Tate模型用于分析长杆侵彻陶瓷靶的适用性.Hohler等(1995)运用闪光X射线照相发现钨合金杆在侵彻陶瓷时侵蚀情况与金属靶类似,且准定常模式下杆弹侵蚀速率与金属靶中相近. 因此,Alekseevskii-Tate模型适用于分析陶瓷靶抵抗长杆侵彻. 然而,由于陶瓷属于脆性材料, 模型中靶体阻力$R_{\rm t}$的描述与确定比金属靶更加困难, 下面对此进行详细讨论.

Rosenberg和Yeshurun(1988)最早发现靶体阻力$R_{\rm t}$与陶瓷压缩强度有关. Rosenberg和Tsaliah(1990)通过实验得到陶瓷开始侵彻的阈值速度$V_{\rm c} $,结合杆弹材料强度$Y_{\rm p} $和阈值速度关系式$V_{\rm c} = \sqrt{{2\left| {R_{\rm t} - Y_{\rm p} } \right|} / {\rho _{\rm p} }} $,计算获得陶瓷靶体阻力$R_{\rm t} $, 发现两组陶瓷AD85和BC90G的$R_{\rm t} $值非常接近平板撞击实验所测的材料Hugoniot弹性极限 $(HEL)$,进而认为在分析陶瓷靶抵抗长杆侵彻时可取$R_{\rm t} \approx HEL$.Subramanian和Bless(1995)利用闪光X射线照片分析钨杆在AD995陶瓷靶中侵彻速度得到的$R_{\rm t} $值同样接近其HEL值. Behner等(2008)用金杆撞击SiC陶瓷得到开始侵彻阈值速度对应的压力显著低于SiC的HEL值,此速度附近由于发生界面击溃向长杆侵彻的转变导致靶体阻力降低.需说明的是, Rosenberg(1993)建议,陶瓷等脆性材料的Hugoniot弹性极限需基于Griffith失效准则而非Tresca或vonMises屈服准则推导, 陶瓷HEL与屈服强度$\sigma _{\rm yt} $的关系为

$$ HEL= \dfrac{1 - \nu }{\left( {1 - 2\nu }\right)^2}\sigma _{\rm yt} (48) $$

虽然存在不同程度的差异, 但不难看出陶瓷的靶体阻力$R_{\rm t}$与其Hugoniot弹性极限相近. 与之相比较的是, 金属靶的$R_{\rm t}$大约是其$HEL$值 (由式(38)求得)的3$\sim $4倍 (Tate 1967).Strenberg(1989)认为该差异主要是由材料的韧性导致,陶瓷材料更容易在弹头前端形成破坏, 故靶体阻力更小. Hauver等(1992)指出, 陶瓷靶阻力受靶体破坏形式影响:高速下侵彻速度超过主要裂纹 (锥裂纹)传入陶瓷速度,故在弹体前端未产生破坏; 而当速度低于2km/s时, 主要裂纹与次要裂纹(翼型裂纹)共同削弱陶瓷靶防护性能.

准静态空腔膨胀模型和动态空腔膨胀理论在岩石、金属、混凝土和玻璃等靶材的高速侵彻问题中已有广泛应用.由于存在裂纹和破碎, 陶瓷靶的动态响应理论分析更加复杂.陶瓷材料拉伸强度显著低于其压缩强度,故当环向应力达到其拉伸强度时有径向裂纹产生. Forrestal和Longscope(1990)考虑拉伸裂纹, 在陶瓷靶的弹性区和塑性区之间加入了破碎区,推导出了球形空腔膨胀所需的准定常压力$R_{\rm t} $. Satapathy和Bless(2000)利用双曲线压剪关系 (Johnson-Holmquist类型本构 (Johnson & Holmquist 1994))同时考虑拉伸裂纹生成,推导了脆性陶瓷的准静态空腔膨胀压力. Satapathy(2001)进一步利用动态空腔膨胀理论研究半无限脆性陶瓷靶的动态响应,将陶瓷靶内响应区由内向外划分为空腔区、粉碎区、径向裂纹区、弹性区和未扰动区,如图33所示. Galanov等(2008)在球形空腔膨胀模型的基础上考虑材料的可压缩气孔和粉末,用更一般的材料孔隙率表达各区体积应变率,从而避免了Mohr-Coulomb准则中较难确定的破碎材料参数.

图33   空腔膨胀模型在陶瓷靶抗长杆侵彻中的响应区示意图 (Satapathy 2001)

   

基于准静态空腔膨胀模型和Alekseevskii-Tate模型, 魏雪英和俞茂宏(2002)李金柱等(2014)翟阳修等(2017)分析了陶瓷靶体阻力$R_{\rm t} $与撞击速度$V$的关系. 分析表明: 在较低的撞击速度(小于1.5km/s)下, 陶瓷靶体强度可取$HEL$值; 撞击速度在一定范围(1.5$\sim$3.0km/s) 内, 陶瓷靶体阻力接近恒值;在更高的速度范围(3.0$\sim $5.0km/s) 内,靶体阻力随撞击速度呈近似线性衰减.

8.2 界面击溃

长杆侵彻陶瓷靶的一个典型现象为长杆与陶瓷靶接触时形成陶瓷锥,锥裂纹迅速延伸到陶瓷靶与背衬板的界面处,导致陶瓷靶在长杆尚未穿透时已经破碎飞溅而丧失防护能力.但当撞击速度低于某一速度时,弹体材料在陶瓷表面径向流动、弹体发生质量侵蚀同时速度下降、陶瓷保持结构完整无明显侵彻破坏.

Hauver等(1992)最早将上述现象称为界面击溃 (interface defeat),而Rosenberg和Tsaliah(1990)早前发现的陶瓷开始侵彻的阈值速度$V_{\rm c} $被定义为界面击溃向长杆侵彻转变的临界速度. 此后, Lundberg等(Andersson et al. 2007; Lundberg & Lundberg 2005; Lundberg et al. 2000, 2006,2013)分别对界面击溃转变速度以及不同陶瓷材料、长杆弹头部形状和尺寸效应对界面击溃效应的影响开展了一系列实验、理论和模拟研究.Johnson和Holmquist (Holmquist & Johnson 2003, 2005; Johnson & Holmquist 1994; Johnson et al.2003)提出了描述陶瓷材料动力学响应的本构模型,并运用CTH程序模拟了陶瓷靶界面击溃. Anderson等 (Anderson & Walker 2005; Anderson et al. 2006, 2008, 2011b; Behner et al.2006, 2008, 2011; Holmquist et al.2010)对界面击溃的理论分析模型、约束、失效波和预破坏对界面击溃的影响以及界面斜击溃进行了分析.Li等 (Li & Chen 2017, Li et al. 2014,2015b)针对不同弹体头形和斜击溃提出了理论分析模型并对界面击溃转变速度进行了分析.谈梦婷等(2016)通过数值模拟研究了不同弹体头形、盖板厚度和预应力对界面击溃的影响.Zhang等(2017)结合陶瓷锥裂纹模型和翼型裂纹扩展模型建立了陶瓷靶界面击溃的损伤演化模型.

谈梦婷等(2019)从实验、理论和数值模拟三方面全面介绍了界面击溃领域的最新研究进展,然而对于研究中的部分突出问题和研究热点未展开深入讨论. 因此,本节主要从界面击溃转变速度、界面击溃的影响因素和斜界面击溃方面进行讨论.

8.2.1 界面击溃转变速度

通过对钨和钼长杆侵彻不同陶瓷的实验与对应的数值模拟, Lundberg等(Lundberg et al. 2000, Westerling et al.2001)发现在无明显侵彻发生的低速区和侵彻速度与撞击速度呈线性的高速区之间,存在狭窄的转变速度区. 转变区内弹体先驻留 (dwell)一段时间 (如图34), 之后以更低的速度侵彻靶体.

图34   界面击溃驻留现象 (Westerling et al. 2001)

   

Anderson等 (Anderson & Walker 2005, Behner et al. 2008,Behner et al. 2011, Holmquist et al.2010)在实验和模拟中也发现了上述现象. Li等(2015b)由此定义了长杆撞击陶瓷靶的3种变形模式,撞击过程中弹体头阴影部分为转变区,曲线由Alekseevskii-Tate模型计算得部和尾部速度的典型变化方式见图3.

Westerling等(2001)结合Alekseevskii-Tate模型对上述现象进行了初步解释:Alekseevskii-Tate模型中$R_{\rm t} - Y_{\rm p}$与侵彻速度$U$的关系可由式(42)表示,侵彻速度的变化可以理解为由靶体阻力的变化所导致. 根据图35所示的实验结果, $R_{\rm t} - Y_{\rm p}$在转变区内由16.5GPa突降至4.2GPa而后保持恒定,故侵彻速度也对应地表现为在转变区内显著变化而在高速下保持恒定.Behner等(2008)用金杆撞击SiC陶瓷的实验恰好证实了转变速度附近靶体阻力的突降.

图35   不同约束下侵彻速度随撞击速度的变化的实验结果(Westerling et al.2001)

   

Lundberg等(2000)通过讨论转变现象发生时轴向应力的可能范围从而确定转变区的速度范围.假设弹体为具有密度$\rho _{\rm p} $、屈服强度$\sigma _{\rm yp}$、体积模量$K_{\rm p} $的理想弹塑性材料,忽略初始瞬态阶段的压力陡峰, Lundberg(2000)建立了界面击溃时陶瓷靶表面的压力分布模型,其中最大压力可表示为

$$ p_0 \approx q_{\rm p} \left( {1 + \dfrac{1}{2\alpha }+ 3.27\beta } \right) (49) $$

其中, $q_{\rm p} =\dfrac{1}{2}\rho _{\rm p} v_{\rm p}^2 $为动压, $\alpha = {K_{\rm p} }/ {q_{\rm p} }$和$\beta = {\sigma _{\rm yp} }/{q_{\rm p}}$分别为压缩性和强度项的系数.

Lundberg等(2005)用钨杆撞击不同SiC陶瓷的实验表明,陶瓷靶表面的最大压力与撞击速度的二次方以及剪切强度均成正比,从而验证了上述压力分布模型的合理性. 值得注意的是,当忽略材料压缩性时 $(\alpha \to \infty )$, 上式变为$p_0 \approx q_{\rm p} \left( {1 + 3.27\beta } \right)$,而由Alekseevskii-Tate模型可得$p_0 = q_{\rm p} \left( {1 + \beta }\right)$, 因此界面击溃时强度影响比长杆侵彻大3.27倍. 此外,Anderson等(2011)认为消除初始冲击的高应力将提高转变速度,这也是采用前置金属盖板的原因.

此外, Lundberg等(2000)建议从界面击溃向侵彻转变对应的最大压力$p_0$范围为$$\left( {1.30 + 1.03\nu } \right)\sigma _{\rm y} \leq p_0 \leq2.85\sigma _{\rm y} (50) $$

式中$\nu $和$\sigma _{\rm y}$分别为陶瓷材料的泊松比与屈服强度. 其中,下边界通过Boussinesq弹性压力方程求得, 上边界由塑性滑移线方程确定,联立式(49)和式(50)即可得到界面击溃转变速度的区间.

Li等(2015b)认为,当撞击压力小于Hugoniot弹性极限时陶瓷材料仅发生弹性变形,故建议将下边界修改为$HEL$, 即转变对应的最大压力$p_0$的范围变为$HEL \leq p_0 \leq 2.85\sigma _{\rm y} $,转变速度的区间对应可表示为

$$ \sqrt {\dfrac{2HEL - 6.54\sigma _{\rm yp} }{\rho _{\rm p} }} \leq v_0 \leq \sqrt {\dfrac{5.7\sigma _{\rm y0} - 6.54\sigma_{\rm yp} }{\rho _{\rm p} }} (51) $$

在此基础上, Li等(2015b)还分析了界面击溃转变过程中靶体强度和弹体速度的变化情况,得到了界面击溃向侵彻转变时间的表达式.

8.2.2 界面击溃的影响因素

进一步研究发现, 影响界面击溃转变速度的主要因素包括:弹体与靶体的材料性质、靶体结构和约束、尺度效应以及弹体几何.

(1) 弹体与靶体的材料性质

Lundberg和Lundberg(2005)分析不同SiC陶瓷侵彻实验结果后认为,不同弹靶材料组合对应一个特定的界面击溃转变速度.控制其他变量而靶材料不同的4组实验, 转变速度从1500m/s(SiC-N)变化到1600m/s (SiC-HPN). Lundberg和Lundberg(2005)认为,陶瓷靶硬度 (对应剪切屈服强度)对转变速度影响不明显,相对而言陶瓷靶的断裂韧性对于界面击溃更为重要.这可能是因为陶瓷等脆性材料的主要失效方式为破碎而非塑性流动.

对于弹体材料, Behner等(2013)以及Aydelotte和Schuster(2015)等通过实验分析认为,弹体材料的强度和密度对界面击溃的影响显著.

(2) 靶体结构

金属盖板是界面击溃实验中常用的靶体结构. Holmquist等(2010)的实验表明,增加铜盖板能使金杆撞击SiC-N陶瓷转变速度从822m/s增至1538m/s.Behner等(2016)最新的正向弹道实验也表明增加盖板能显著提高SiC陶瓷对钨合金杆界面击溃的转变速度.

Lundberg等 (Lundberg & Lundberg 2005; Lundberg et al. 2000,2006; Westerling et al. 2001)和Anderson等 (Anderson et al. 2011a,Behner et al. 2011)讨论了金属盖板对提高界面击溃转变速度的作用:盖板一方面扩大杆弹头部面积从而分散初始载荷,另一方面延长杆弹材料对陶瓷靶的作用时间从而可避免撞击面产生的拉伸应力导致靶板过早失效.

对于盖板尺寸, Holmquist等(2010)通过模拟发现盖板直径对转变速度和转变时间有轻微影响. 谈梦婷等(2016)的模拟结果表明转变速度随盖板厚度的增大而增大, 但Behner等(2016)的实验结果表明最佳盖板厚度为弹体直径的一半.

(3) 靶体约束

大量实验均采用过盈配合的约束对陶瓷施加预应力,由于陶瓷材料的强度和破碎性能皆存在应力相关性,因此推测界面击溃转变速度受约束力影响.

Holmquist和Johnson(2003)的模拟结果显示,转变速度随约束力的增大而增大. Anderson等(2007)通过实验对比了钨合金长杆撞击有约束和无约束SiC-B陶瓷的界面击溃速度,与无约束陶瓷的转变速度(1027m/s)相比, 有约束陶瓷的转变速度(1549m/s) 明显提升(Lundberg & Lundberg 2005). 此外,转变速度增大与陶瓷表面最大压力改变相联系(1027m/s对应13GPa,而1549m/s对应26GPa),增大200MPa的约束力让界面击溃时陶瓷表面载荷翻倍.

然而, Holmquist等(2010)实验得到的无预应力附加盖板的SiC-N陶瓷阻力(约24GPa)与Lundberg等 (Andersson et al. 2007, Lundberg & Lundberg 2005)有预应力附加盖板的SiC-B陶瓷阻力 (约26GPa)相近,进而认为预应力影响较小. Lundberg等(2013)认为尺度效应导致了预应力和约束影响减弱,故强约束大尺寸靶和无约束小尺寸靶可能得到相近的转变速度.

(4) 尺度效应

Anderson等(2007)Holmquist等(2010)Behner等(2011)Lundberg等(2013)的研究中都关注了界面击溃的尺度效应. 实验结果表明,相同弹靶材料组合下, 较大靶体的界面击溃转变速度更低.

Anderson等(2007)对此作了初步的理论解释:假设转变速度的上限受锥裂纹形成和发展的控制,由于裂纹阻力随尺度减小而增大, 故小尺寸靶中裂纹延伸更加困难,因而发生侵彻所需撞击速度越大.

Lundberg等(2013)根据上述假设建立了包含界面击溃条件下锥裂纹发展的理论分析模型,模型预测转变速度与尺寸的-1/2次方成正比.小尺寸靶的实验结果支持上述模型,而大尺寸靶实验则表现出转变速度与尺寸无关. 因此,实际应用中应谨慎考虑尺寸效应的影响.

(5) 弹体头部形状

Lundberg等(2006)通过实验研究了弹体头部形状对界面击溃的影响,锥头弹对有盖板陶瓷靶的界面击溃转变速度低于平头弹/柱形弹. 然而,谈梦婷等(2016)的模拟结果则显示,平头、球头和锥头长杆弹的界面击溃转变速度依次升高,同时驻留时间也依次延长.

Li等(2014)基于Alekseevskii-Tate模型建立了不同头形的界面击溃分析模型,模型预测锥头弹体的动能损失速度比平头弹更慢,然而模型未能反映弹体头部形状对转变速度的影响.

8.2.3 界面斜击溃

以上研究均针对长杆正碰撞陶瓷靶的界面击溃现象,实际应用中斜碰撞更加普遍, 不少研究者已对陶瓷靶斜撞击进行了一系列的研究 (Anderson et al. 2011a, Hetherington & Lemieux 1994, Hohler et al. 2001, Lee, 2003, Li & Chen 2017, Sadanandan & Hetherington 1997, Zaera & Sánchez-Gálvez 1998).

Anderson等(2011a)对斜界面击溃进行了实验和理论的研究,实验中金杆以900$\sim $1650m/s的速度撞击倾角范围为30$^\circ$$\sim$60$^\circ$的素陶瓷和含盖板陶瓷. 实验结果表明,杆弹斜撞击素陶瓷发生驻留时的速度高于正撞时的速度,素陶瓷驻留时间随倾角的增大而延长.

Li和Chen(2017)提出了斜界面击溃的理论分析模型. 如图36, 斜撞条件下弹靶接触面形状变为半长轴为 $R/{\cos \theta }$的椭圆, 根据Alekseevskii-Tate模型进行简单近似,可以得到弹尾速度随时间变化与倾角$\theta $之间的关系

$$v = v_0 - \dfrac{1}{\cos \theta }\dfrac{\sigma _{\rm yp} }{\rho _{\rm p} l_0 }t (52) $$

图36   正撞 (a)和斜撞 (b)下界面击溃及其压力分布意图 (Li & Chen 2017)

   

忽略式中的可压缩项, 图36中的压力分布可以近似表示为

$$ P_{\rm r} = P_0 \sqrt {1 - \left( {r/ {r_{\rm c} }}\right)^2} (53) $$

根据正撞和斜撞的能量守恒关系$P'_0 \pi r_{\rm c} \left( {r_{\rm c} \cos \theta } \right) = P_0 \pi r_{\rm c}^2 $, 故斜撞击的最大压力$P'_0 $可表示为

$$ P'_0 = {P_0 } / {\cos \theta } (54) $$

代入Li等(2015b)提出的转变速度确定公式(式(51)和式(48))可知,界面斜击溃转变速度与倾角$\theta $近似呈$1 /{\sqrt {\cos \theta }}$的关系, 而非Anderson等(2011b)所认为的$1/ {\cos \theta }$的关系.

9 非理想长杆侵彻

前文关注了理想状态长杆弹垂直侵彻半无限厚靶板. 然而,在实际的武器研制与装甲设计中,非理想长杆侵彻问题更普遍从而更有研究价值. Goldsmith(1999)对弹/靶非对称作用的诸多研究成果进行了综述,但其论述对象主要为刚性弹和短粗弹体.本节将重点关注非理想长杆侵彻的研究工作,包括长杆侵彻有限厚靶和非对称长杆侵彻. 为避免混淆本文论述采用与,Goldsmith(1999)综述中相同的弹/靶作用姿态角定义,如图37所示. 其中, 攻角$\alpha$定义为弹体速度矢量与弹体轴线方向的夹角, 斜角$\beta$定义为弹体速度矢量与靶体表面法线方向的夹角(部分文献中定义的速度矢量与靶体表面夹角为倾角$\bar {\beta }$,即斜角$\beta $的余角).

图37   弹靶作用姿态角的定义 (Goldsmith 1999)

   

9.1 长杆侵彻有限厚靶

长杆对有限厚靶的侵彻由于涉及非定常侵彻、靶板后表面导致的侵彻阻力下降以及弹体到达后表面前靶内不同失效机制等问题,较半无限厚靶侵彻更为复杂. Stilp和Holher(1990)拍摄到的$L/D=10$的钢杆以2.03km/s的速度侵彻有限厚钢板的弹坑如图38所示.图中靶板背面的鼓胀以及拉伸失效的特征体现出了与无限厚靶侵彻的显著差异,此外还能从图中观察到弹坑壁上残留的反向流动的弹体材料以及靠近靶板背面时弹坑直径的轻微增大.长杆侵彻有限厚靶问题的复杂性大大增加了理论分析的难度. Walker(1999)Chocron等(2003)提出的长杆侵彻有限厚靶的分析模型对靶板背面鼓起的现象进行了解释,然而该模型强烈依赖数值模拟结果因而不具有预测能力.

图38   钢杆撞击钢板形成的弹坑形貌 (Stilp & Hohler 1990)

   

武器设计者和装甲工程师最关心的问题,一个是长杆侵彻一定厚度靶后的剩余速度$V_{\rm r} $,另一个是长杆贯穿一定厚度靶所需的最低速度 (弹道极限速度) $V_{\rm bl} $. 因此, 相关研究也可对应地分成两类:一类重点关注弹体剩余速度$V_{\rm r} $与初始撞击速度$V_0 $的关系,另一类则旨在获得靶厚与弹道极限速度$V_{\rm bl} $的关系.

9.1.1 弹体剩余速度$V_r $

Gragarek(1971)对长杆侵彻有限厚装甲钢板的大量实验数据进行整理,提出如下剩余速度的经验公式

$$\dfrac{V_{\rm r} }{V_{\rm bl} } = \dfrac{1.1y^2 + 0.8y+ 2y^{0.5}}{1 + y} (56) $$

式中, $y = {V_0 } / {V_{\rm bl} }- 1$. 该式的适用范围为$1 < {V_0 }/ {V_{\rm bl} } < 2.5$,在更高的撞击速度下 $({V_0 } / {V_{\rm bl} }> 2.5)$, 剩余速度几乎等于撞击速度, 这是由于贯穿靶板所用时间很短,速度降低可以忽略.

Anderson等(1999a)对不同强度钢杆贯穿装甲钢板的实验数据的拟合与Gragarek(1971)的经验公式具有相同的形式, 但$y^2$,$y$和$y^{0.5}$三项的系数分别为0.9, 1.3和1.6.

Lambert(1978)基于解析分析提出了另一种长杆侵彻剩余速度的半经验公式

$$ \dfrac{V_{\rm r} }{V_{\rm bl} } = k_0 \cdot \left[{\left( {\dfrac{V_0 }{V_{\rm bl} }} \right)^m - 1} \right]^{1/m} (57) $$

式中$k_0 $和$m$为根据弹靶组合确定的经验参数,对钢杆侵彻装甲钢靶, 可取$k_0 = 1$, $m = 2.5$. Burkins等(1996)测量钨合金与贫铀杆弹侵彻Ti/6Al/4V发现, 式(2)中取$k_0 =1$和$m = 2.6$能较好地拟合实验数据. Rosenberg和Deke(2012)通过模拟进一步验证了上述公式的可靠性, 他们还发现:参数$m$决定了撞击速度靠近弹道极限速度$V_{\rm bl}$时曲线的陡峭程度, 高速下弹体剩余速度$V_{\rm r}$接近初始撞击速度$V_0 $, 曲线对$m$值不敏感.

图39比较了Gragarek(1971)Anderson等(1999a)Lambert(1978) 3组经验公式对钢杆贯穿装甲钢板的描述,3组曲线均表现出低速时陡峭, 高速时趋近$V_{\rm r} = V_0 $的趋势.3组曲线在低速时较接近, 但在高速时Lambert的曲线更迅速趋近$V_{\rm r}= V_0 $. 考虑到经验公式的物理描述和参数数量, 推荐使用Lambert关系.

图39   钢杆贯穿装甲钢板的剩余速度的3组经验公式比较

   

Anderson等(1992a)编纂的侵彻实验数据库对不同来源的长杆侵彻有限厚靶的剩余弹体速度实验进行了总结,讨论了弹体剩余速度、长度、质量之间的相互关系以及材料参数对它们的影响.其中3个现象值得关注: (1)虽然随剩余速度的增大弹体剩余长度增大,然而在很高的剩余速度下弹体仍有相当部分被侵蚀 $({V_{\rm r} }/{V_0 }= 0.9$时最硬的弹体仍有50%被侵蚀); (2)相同情况下,弹体的相对剩余质量高于相对剩余长度,这可能是由于弹体在侵彻过程中的头形钝化为蘑菇头导致弹体直径增大;(3)部分实验反映出弹体剩余速度与弹体硬度无关,然而弹体剩余长度和质量均表现出与弹体硬度有关.

9.1.2 弹道极限速度$V_bl $

确定长杆贯穿一定厚度靶所需的弹道极限速度$V_{\rm bl} $有两种方法,一种是采用上述剩余弹体速度实验,通过实验数据的拟合曲线推测弹道极限速度; 另一种则是进行多组重复实验(至少6组), 取贯穿率为50%的速度$V_{50} $为弹道极限速度$V_{\rm bl} $.

Anderson等(1992a)整理了不同弹靶组合下弹道极限速度$V_{\rm bl}$的实验数据, 发现$H /L-V_{\rm bl} $曲线 (即${H_{\rm bl} } /L-V_0$曲线, $H_{\rm bl}$为阻止给定撞击速度的杆弹所需的最小靶板厚度)与半无限厚靶侵彻的$P /L-V_0 $曲线相似. 由于靶板后表面失效的影响, ${H_{\rm bl} }/L$略高于$P / L$, 在1$\sim $3km/s速度范围内, $H_{\rm bl}$约比$P$高出1$\sim $2倍杆径. 根据上述特征, Anderson等(2015)结合对长杆侵彻无限厚靶实验数据的拟合结果, 提出了如下的长杆侵彻有限厚靶经验公式

$$ \left. {\begin{array}{l} \dfrac{H_{\rm bl} }{L} = \dfrac{P}{L} + \dfrac{k_1 D}{L} \\ \dfrac{P}{\mu L} = a_1 + \dfrac{a_2 }{1 + 10^{a_3 \cdot \left( {a_4 - \bar{V}} \right)}},\qquad \bar {V}= \left( {\dfrac{\rho _{\rm p}V^2}{\sigma _{\rm t} }}\right)^{0.20}\mu ^{ - 0.14} \\ \end{array}} \right\} (58) $$

式中, $a_i $是根据实验结果拟合的参数, $\sigma _{\rm t} $为靶板的等效流动应力, $k_1 $通常取1.2. Rosenberg和Dekel(2012)认为, 长杆侵彻有限厚靶与无限厚靶的差异随撞击速度增大而减小,但即使是在3km/s速度下该差异仍存在. 因此, 上式中$k_1$取为撞击速度的函数更为恰当. Anderson等(2015)指出,式(58)仅是对长杆侵彻有限厚靶中多种失效模式的简单平均,对薄板的花瓣形破坏和厚靶的绝热剪切带等一些失效模式不能准确描述.

9.2 非对称长杆侵彻

非对称长杆侵彻主要包括:长杆斜侵彻、长杆跳飞、长杆侵彻运动靶以及带攻角长杆侵彻.姿态角和相对速度变化将直接影响侵彻能力,同时作用于弹体头部的非对称力将使弹体轨迹和弹体本身发生弯曲,甚至引起弹体跳飞从而大幅降低侵彻能力.

9.2.1 长杆斜侵彻/贯穿

Hohler等(1978)研究了$L/D = 10$钨合金杆撞击不同厚度的倾斜钢板,考虑到长杆侵彻斜靶板时沿撞击速度方向的厚度为$H/ {\cos \beta }$,长杆斜贯穿有限厚靶板后剩余长度和剩余速度随无量纲靶厚$H/ {(L\cos\beta })$的变化规律与正撞击相似, 同时斜撞击的${H_{\rm bl} }/{\cos\beta }$高于正撞击的$H_{\rm bl} $. 此外, 从如图40所示的钨合金杆撞击倾斜钢板的X射线照片中能明显观察到,长杆穿透斜钢板后发生部分断裂, 未断裂部分发生弯曲,弯曲长杆在撞向后面靶板时具有较大偏航角导致其侵彻能力显著降低.因此, 将靶板倾斜放置能有效提高其抗侵彻性能. 此外, Hohler等(2001)Lee(2003)进一步研究了陶瓷/金属复合靶抵抗长杆斜侵彻的性能.

图40   钨合金杆撞击倾斜钢板的X射线照片 (Hohler et al. 1978)

   

9.2.2 长杆跳飞

随着斜角$\beta $增大, 作用于长杆头部的非对称力可能导致弹体跳飞.Tate(1979)将此过程看作是撞击面对杆弹头部的非对称力导致长杆绕质心转动,进而结合Alekseevskii-Tate模型建立力矩关系求出了如下跳飞条件

$$\tan ^3\beta > \dfrac{2\rho _{\rm p} V^2}{3Y_{\rm p} }\cdot \left( {\dfrac{L^2 + D^2}{LD}} \right) \cdot \dfrac{V}{V -U} (59) $$

Tate(1979)跳飞模型的最大缺陷在于假设弹体不发生弯曲变形,然而长杆在斜撞击时变形严重, 弹靶接触区形成塑性铰. Senf等(1981)在长径比为10的低碳钢杆从装甲钢板上跳飞的实验中发现,速度为968m/s、斜角为75$^\circ$时长杆发生跳飞,实验中高速摄影照片和数值模拟结果均能看到明显的塑性铰与弹体弯曲.

Rosenberg等(1989)建议非对称力仅作用在弹体被侵蚀的质量上,因此假设非对称力等于靶体阻力$R_{\rm t} $与弹靶接触面的乘积,分析得到的跳飞最小斜角的判据为

$$ \tan ^2\beta > \dfrac{\rho _{\rm p} V^2}{R_{\rm t} }\cdot \dfrac{V + U}{V - U} (60) $$

Rosenberg等(1989)的跳飞模型由于考虑塑性铰而非转动惯量,因而模型中无杆长度项, 这与Tate(1979)的跳飞模型所预测的最小跳飞角随长径比增大而增大的结论有本质差异.此外, 模型中强度控制参数为靶体阻力$R_{\rm t} $而非Tate(1979)模型中采用的杆强度$Y_{\rm p} $.

Rosenberg等(1989)开展了$L /D = 10$的WHA杆以0.65$\sim$1.3km/s撞击$\beta = 55^\circ\sim 75^\circ$的RHA靶板的实验,实验数据与模型预测结果如图41所示. 模型较好地解释了实验结果,临界跳飞角 (临界跳飞角$\beta _{\rm c}$定义为不等式取等号时对应的角度值)确定了长杆跳飞的边界,侵彻和跳飞的数据点分布在曲线两侧.

图41   WHA杆撞击RHA靶板的实验数据以及Rosenberg跳飞模型预测结果 (Rosenberg et al. 1989)

   

由于临界跳飞角随撞击速度减小而减小,故理论上必存在一个最小临界跳飞角. Rosenberg等(2007)引入Alekseevskii-Tate模型中的弹尾临界速度$V_{\rm c} = \sqrt{{2\left( {R_{\rm t} - Y_{\rm p} } \right)} /{\rho _{\rm p} }} $,提出了对应于零侵彻 $(U = 0, V_0 = V_{\rm c} )$的最小斜角$\beta_{\rm c}^{\min } $

$$\tan ^2\beta _{\rm c}^{\min } = \dfrac{\rho _{\rm p}V_{\rm c} ^2}{R_{\rm t} } = 2\left( {1 - \dfrac{R_{\rm t} }{Y_{\rm p} }} \right) (61) $$

由上式可以看出, 最小斜角$\beta _{\rm c}^{\min } $仅依赖于弹靶强度之比. 对${R_{\rm t} }/ {Y_{\rm p}}$取典型值1/3, 则$\beta _{\rm c}^{\min } = 49^\circ$.

Lee等(2002)通过实验和模拟研究了薄靶上的长杆跳飞.由于薄靶后表面的影响, 杆弹更倾向于侵彻入靶体,因此薄靶的临界跳飞角相比半无限厚靶更大. 同时, Lee等(2002)的模拟结果与Rosenberg跳飞模型的预测结果存在相似性,薄靶的临界跳飞角$\beta _{\rm c} $比模型预测大3$^\circ$左右.

9.2.3 长杆侵彻运动靶

由前文分析可知, 长杆的临界跳飞角强烈依赖于撞击速度. 由此可以推测,与长杆运动相同的方向推动靶板从而降低弹/靶相对速度,可以使长杆更容易发生跳飞. 图42展示了Rosenberg等(2009)开展的长杆在运动钢板上的跳飞实验.钨合金长杆以1.0km/s的速度和63$^\circ$的斜角撞向用一层炸药驱动的以270m/s的速度运动的装甲钢板并发生跳飞,而相同条件下的长杆对静止钢板的撞击将发生穿透.

图42   钨合金长杆从运动钢板上跳飞 (Rosenberg et al. 2009)

   

反应装甲对长杆弹的抵抗正是利用了上述机制.虽然爆炸反应装甲由于对聚能射流的有效抵抗已应用于坦克的附加装甲,但反应装甲抵抗长杆侵彻的研究仍处于初期. Shin和Yoo(2003)通过模拟发现薄板以低至200m/s的速度背离长杆运动方向运动将导致长杆显著破坏,而与长杆相向运动的薄板与静止薄板均对长杆造成轻微破坏.Rosenberg和Dekel(2004)综合运用实验、数值模拟和解析模型对运动钢板抵抗长杆侵彻的机制进行了较系统的研究.

Rosenberg和Dekel(2004)将钨合金长杆分别以不同的倾角和$V_{\rm p} =1.4$km/s的速度撞向以$V_{\rm t} =0.43$km/s运动的厚4.3mm的装甲钢板,发现撞击倾角仅相差5$^\circ$的两长杆出现了完全不同的两种破坏情况:倾角$\bar {\beta }= 35^\circ$的长杆发生严重破坏, 而$\bar {\beta }=40^\circ$的长杆则发生轻微破坏.根据模拟图像中看到的剪切钢带的不同方向, Rosenberg和Dekel(2004)推测长杆的破坏程度与长杆对靶板的临界撞击速度有关,进而提出了如下考虑弹靶相对运动的理论分析模型.

假设钢板运动速度$V_{\rm t} $垂直于钢板表面, 故弹靶相对速度$V_{\rm rel} $即可表示为

$$ V_{\rm rel} = V_{\rm p} - \dfrac{V_{\rm t} }{\sin \bar{\beta }} (62) $$

通过弹靶相对速度$V_{\rm rel} $大于0而小于临界撞击速度$V_{\rm c} $,Rosenberg和Dekel(2004)提出的移动靶板使长杆严重破坏的条件为

$$ \sin \bar {\beta } > \dfrac{V_{\rm t} }{V_{\rm p} } >\left( {1 - \dfrac{V_{\rm c} }{V_{\rm p} }} \right) \cdot \sin\bar {\beta } (63) $$

上述条件在 $({V_{\rm t} }/{V_{\rm p} }$, $\bar {\beta})$平面上表现为两条曲线之间的“破坏区”,包含导致长杆严重破坏的所有实验条件. “破坏区”上边界固定 $({V_{\rm t} } / {V_{\rm p} }= \sin \bar {\beta })$,下边界根据弹靶组合的临界撞击速度$V_{\rm c} $变化. Rosenberg和Dekel(2004)用更高硬度的钢板重复$\bar {\beta }= 40^\circ$的实验,长杆由轻微破坏变为严重破坏, 这与高硬度钢板$V_{\rm c}$更高导致破坏区下边界降低相对应. 此外,运动靶板的厚度对其抗侵彻性能亦有影响, 越薄的板其后表面影响越大,故引起长杆严重破坏所需的靶板速度也越高.

9.2.4 带攻角长杆侵彻

实际的侵彻实验中, 弹体受扰动后会以一定攻角$\alpha $撞击靶体.Bless等(1978)Silby等(1983)的实验数据表明,存在一个临界攻角$\alpha _{\rm c} $,在低于此值时攻角对侵彻深度几乎没有影响. Silby等(1983)提出,当长杆尾部不与弹坑壁碰撞时长杆侵彻能力不受攻角影响,因此控制临界攻角$\alpha _{\rm c} $的几何约束条件为

$$ \alpha _{\rm c} = \sin ^{ - 1}\left[ {{\left( {D_{\rm c} - D_{\rm p} } \right)} /{2L}} \right] (64) $$

式中,$D_{\rm c} $和$D_{\rm p} $分别为弹坑和杆弹的直径.

应用式(64)预估临界攻角$\alpha _{\rm c} $所需的弹坑直径$D_{\rm c}$, 可通过经验公式 (式(4)和式(5))或理论预测 (式(44))获得. 实际上,在侵彻过程中弹坑直径会发生变化. 如图43所示,长杆在侵彻过程中对弹坑壁产生挤压而形成挖槽,弹尾在弹坑内来回反弹导致弹坑扩大, 导致侵彻能力显著降低.

图43   中等攻角长杆侵彻的典型弹坑形状 (Bjerke et al. 1992)

   

根据式(64), 对于长径比$L / D$为10$\sim $20的长杆,临界攻角约为1.5$^\circ \sim 3 ^\circ$. 因此, 对于装甲设计师来说,采用附加装甲使长杆产生几度的攻角,是提高装甲抗长杆侵彻能力的一个重要的设计思路.

Bless等(1978), Yaziv等(1992), Bukharev和Zhurkov(1995),Hohler和Behner(1999)的实验表明, 当攻角大于某临界值后,长杆侵彻深度随攻角增大而急速下降. 为解释上述实验结果, Yaziv等(1992)利用Alekseevskii-Tate模型来预测带攻角长杆的侵彻深度,Bukharev和Zhurkov(1995)在Alekseevskii-Tate模型的基础上同时考虑了弹体转动和弹坑对弹体的横向作用力.根据上述模型, 攻角接近临界值时侵彻深度受其有效长度 $(L_{\rm eff}\propto L\cos \alpha )$影响; 而攻角超过临界值时侵彻深度由等效直径$(D_{\rm eff} \propto {D_{\rm p} }/ {\sin \alpha })$控制.

Lee(2000)将带攻角的长杆离散为一系列圆盘,建立了带攻角长杆侵彻的几何模型. 其中, 弹坑直径$D_{\rm c}$由式(44)确定, 长杆侵彻能力的下降与圆盘直径和弹坑重叠部分成正比.Rosenberg等(2006)采用相似思路,根据$n$等分的每一小段与弹坑壁的几何关系确定等效直径$D_{\rm eff}$和有效长度$L_{\rm eff} $, 将$D_{\rm eff} $和$L_{\rm eff}$代入Walker等(2001)关于长杆无量纲侵彻深度的拟合经验公式求得侵彻深度.

Yaziv等(1992)与Bukharev和Zhurkov(1995)的唯象模型优势在于侵彻深度的预测,然而模型中不包含弹坑尺寸的计算, 因而无法预测临界攻角. Lee(2000)Rosenberg等(2006)的几何模型基于几何关系推导,能同时预测临界攻角和侵彻深度.两类模型中均忽略了前文中提及的侵彻过程中弹坑直径的变化,同时除Bukharev和Zhurkov(1995)模型外均未考虑弹体转动的影响. Kong等(2016b)建立的理论分析模型和数值求解方法考虑了上述两个因素,对临界攻角能进行合理预测, 但却未能预测大攻角长杆的侵彻深度.

10 结语与展望

长杆高速侵彻问题具有强大的军事应用背景, 是穿甲侵彻领域的研究热点.经过半个多世纪尤其是近二十年国内外同行的不懈努力,已取得丰富的研究成果. 本文全面地综述了长杆高速侵彻问题的研究进展,介绍了长杆高速侵彻的基本概念、研究方法和理论模型,并对研究中重点关注的几个突出问题与应用进行了评述.通过对相关文献的调研, 针对长杆高速侵彻问题的研究,作者认为近期可以在以下方面开展工作:

(1) 发展实验技术.利用更先进的设备和技术对传统弹靶组合的实验进行验证,同时针对新弹靶材料、不同弹头形状、撞击姿态和靶体结构开展大速度范围的实验,验证已发现的实验现象 (如侵彻模式转变、界面击溃、弹体自锐),并发现新的侵彻现象和变形失效机制. 值得注意的是,目前实验主要关注长杆高速侵彻的侵彻深度, 对开坑直径和残余弹体长度(质量)等问题还需要进一步关注和研究.

(2) 发展模拟技术. 结合并行计算、多尺度模拟等新兴计算技术,开发更优的网格划分技术和计算方法, 提高计算规模、效率和精度.改进材料本构,建立更符合长杆高速侵彻过程中弹靶变形失效和材料特性的三维数值模拟模型.针对弹靶材料性质影响、长径比效应、侵彻末端作用机理、陶瓷靶和混凝土靶抗长杆侵彻机理等方面继续开展数值模拟,力图加深对侵彻机理的认识, 为构建更完善的理论模型提供依据.

(3) 深入分析弹靶材料性质对长杆高速侵彻的影响.进一步研究靶体阻力$R_{\rm t} $随撞击速度的变化关系,比较陶瓷靶等脆性材料和其他材料的靶体阻力与金属靶体阻力的差异,找寻适用于不同撞击速度和材料性质的具有明确物理意义的靶体阻力表达;再者, 探讨弹体强度$Y_{\rm p} $的物理意义和影响,在更宽弹体强度范围内开展侵彻实验和模拟, 分析最大侵彻深度现象;此外, 探究密度、热软化、绝热剪切等多种材料性质对侵彻能力的影响,考虑其在本构模型和屈服准则中的描述,在理论模型和数值模拟中反映上述性质的影响; 最后,运用无量纲方法整理已有实验和模拟结果, 分析其间的相似关系,对侵彻实验设计具有指导意义.

(4) 研究初始头形和侵彻过程中头形对长杆高速侵彻性能的影响.构造长杆高速侵彻中的弹头形状函数, 建立2D理论分析模型,对长杆弹高速侵彻能力进行更合理的预测;分析侵彻过程中不同头形的形成机理, 讨论不同头形在能量变化上的差异,获得对长杆高速侵彻物理机制的新认识;研究长杆高速侵彻过程中的弹体头形变化, 分析头形演化现象和规律,提出头形演化的临界条件.

(5) 继续研究长径比效应及其作用机理,建立能反映长径比效应的2D理论分析模型;对分段杆开展实验、模拟和理论分析工作,分析连接结构对分段杆侵彻性能的影响, 探索分段杆的最优结构;分析变密度 (梯度变化/周期性变化)杆等新弹体构型的侵彻性能.

(6) 开展更多陶瓷靶抗侵彻实验, 深入分析影响陶瓷靶防护效率的各因素,找寻防护效率高的陶瓷材料和靶体结构;建立考虑裂纹和破碎的陶瓷靶动态空腔膨胀理论与靶体阻力$R_{\rm t}$之间的联系; 改善陶瓷材料本构, 考虑损伤演化和动态破坏,更准确地模拟陶瓷靶抗侵彻过程和界面击溃效应;深入研究界面击溃的宏微观机理, 分析影响界面击溃的各因素,建立各因素与转变速度之间的定量关系.

(7)开展有限厚靶、斜侵彻、跳飞、侵彻运动靶和带攻角长杆侵彻等非理想侵彻问题的研究.这部分问题涉及多种失效机制, 分析难度较大,可以考虑结合实验和模拟对典型现象进行分析,同时建立一系列物理意义明确的理论模型对上述现象做出合理解释和预测.

对以上问题的研究一方面能发展和完善长杆高速侵彻理论,有助于正确认识长杆高速侵彻机理,更准确地分析和预测长杆弹的侵彻能力,另一方面也能为长杆武器的研制以及坦克装甲的设计提供科学的指导,值得科研工作者们共同努力.

致谢

The authors have declared that no competing interests exist.


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. 力学进展, 36: 85-102

DOI      URL      [本文引用: 3]      摘要

In the last decade, the dynamic response of ceramicmaterials and the penetration/perforation of targets of ceramics,ceramic/metal, ceramic/composite and layered ceramics is an activeresearch area. It has applications, especially, in the military field. Relatively little work in thisarea is conducted in China. The present paper introduces therecent advances in this area.Theexperimental techniques, penetration/perforation mechanisms and theoreticalmodels are reviewed. The cavity expansion model in ceramics penetration andthe effect of failure wave are specially addressed. Some research proposalsare made at the end of the paper.

(Chen X W, Chen Y Z.2006.

Review on the penetration/perforation of ceramics targets

. Advances in Mechanics, 36: 85-102).

DOI      URL      [本文引用: 3]      摘要

In the last decade, the dynamic response of ceramicmaterials and the penetration/perforation of targets of ceramics,ceramic/metal, ceramic/composite and layered ceramics is an activeresearch area. It has applications, especially, in the military field. Relatively little work in thisarea is conducted in China. The present paper introduces therecent advances in this area.Theexperimental techniques, penetration/perforation mechanisms and theoreticalmodels are reviewed. The cavity expansion model in ceramics penetration andthe effect of failure wave are specially addressed. Some research proposalsare made at the end of the paper.
[3] 陈小伟, 李继承, 张方举, 陈刚. 2012.

钨纤维增强金属玻璃复合材料弹穿甲钢靶的实验研究

. 爆炸与冲击, 32: 346-354

DOI      URL      [本文引用: 2]      摘要

为具体研究钨纤维增强金属玻璃复合材料的力学特性及其穿甲自锐特 征,开展了相应的准静态和动态力学实验,并用火炮开展了复合材料弹体撞击钢靶的穿甲实验,同时利用金相分析对材料失效模式进行了较系统的识别和分类,并同 静动态实验数据进行比较分析,最后开展了材料自锐剪切失效的机理讨论.实验获得了复合材料的静动态力学特性及其自锐穿甲的形貌,相关分析显示,材料的变形 具有明显的应变率效应,在复合材料弹体侵彻/穿甲过程中,弹体的破坏方式主要表现为局域化的剪切变形和断裂,并呈现出4种自锐剪切失效模式,增强钨纤维也 表现出3类失效破坏模式.

(Chen X W, Li J C, Zhang F J, Chen G.2012.

Experimental research on the penetration of tungsten-fiber/metallic glass-matrix composite material penetrator into steel target

. Explosion and Shock Waves, 32: 346-354).

DOI      URL      [本文引用: 2]      摘要

为具体研究钨纤维增强金属玻璃复合材料的力学特性及其穿甲自锐特 征,开展了相应的准静态和动态力学实验,并用火炮开展了复合材料弹体撞击钢靶的穿甲实验,同时利用金相分析对材料失效模式进行了较系统的识别和分类,并同 静动态实验数据进行比较分析,最后开展了材料自锐剪切失效的机理讨论.实验获得了复合材料的静动态力学特性及其自锐穿甲的形貌,相关分析显示,材料的变形 具有明显的应变率效应,在复合材料弹体侵彻/穿甲过程中,弹体的破坏方式主要表现为局域化的剪切变形和断裂,并呈现出4种自锐剪切失效模式,增强钨纤维也 表现出3类失效破坏模式.
[4] 程兴旺, 王富耻, 李树奎, 王鲁. 2007.

不同头部形状长杆弹侵彻过程的数值模拟

. 兵工学报, 28: 930-933

DOI      URL      [本文引用: 1]      摘要

The processes of penetrating the semi-infinite rolled homogeneous armor (RHA) targets with four kinds of nose shapes of long-rod projectiles were studied by numerical simulation method, the effects of nose shapes on penetration were inspected emphatically. The results show that the depth of penetration (DOP) depends on pronouncedly the iailure mechanism of the rod material, the variation of the nose shapes of long-rod projectiles results in slight difference of the penetration depths at the same condition for high strength material, but the nose profile of long-rod has a certain influence on the breakup of targets, especially on the cross-section of crater in the early stage.

(Cheng X W, Wang F Z, Li S K, Wang L.2007.

Numerical simulation on the penetrations of long-rod projectiles with different nose shapes

. Acta Armamentarii, 28: 930-933).

DOI      URL      [本文引用: 1]      摘要

The processes of penetrating the semi-infinite rolled homogeneous armor (RHA) targets with four kinds of nose shapes of long-rod projectiles were studied by numerical simulation method, the effects of nose shapes on penetration were inspected emphatically. The results show that the depth of penetration (DOP) depends on pronouncedly the iailure mechanism of the rod material, the variation of the nose shapes of long-rod projectiles results in slight difference of the penetration depths at the same condition for high strength material, but the nose profile of long-rod has a certain influence on the breakup of targets, especially on the cross-section of crater in the early stage.
[5] 高光发, 李永池, 黄瑞源, 李平. 2012.

杆弹头部形状对侵彻行为的影响及其机制

. 弹箭与制导学报, 32: 51-54

DOI      URL      [本文引用: 1]      摘要

为探讨不同靶板类型时杆弹头部形状对侵彻行为的影响,对几种头部 形状杆弹进行了数值仿真.研究表明:靶板为4340钢且入射速度较小时,杆弹头部形状对侵彻行为有一定的影响,最优头部形状是半球形,速度较大时,头部形 状只在开坑阶段对侵彻行为造成影响,对弹体的最终侵彻效率影响并不大;靶板为混凝土时,头部形状对侵彻行为有很大的影响,卵形头部弹体的侵彻能力明显强于 其它两种头部形状的弹体;并对其影响机制进行了深入的研究.

(Gao G F, Li Y C, Huang R Y, Li P.2012.

Effect of nose shape on the penetration performance of long-rod penetrator and its mechanism

. Journal of Projectiles, Rockets Missiles and Guidance, 32: 51-54).

DOI      URL      [本文引用: 1]      摘要

为探讨不同靶板类型时杆弹头部形状对侵彻行为的影响,对几种头部 形状杆弹进行了数值仿真.研究表明:靶板为4340钢且入射速度较小时,杆弹头部形状对侵彻行为有一定的影响,最优头部形状是半球形,速度较大时,头部形 状只在开坑阶段对侵彻行为造成影响,对弹体的最终侵彻效率影响并不大;靶板为混凝土时,头部形状对侵彻行为有很大的影响,卵形头部弹体的侵彻能力明显强于 其它两种头部形状的弹体;并对其影响机制进行了深入的研究.
[6] 蒋东, 李永池, 于少娟, 邓世春. 2010.

钨合金长杆弹侵彻约束AD95陶瓷复合靶

. 爆炸与冲击, 30: 91-95

DOI      URL      [本文引用: 1]      摘要

以侵彻深度(depth of penetration,DOP)实验为基础,利用LSDYNA软件进行数值模拟,对钨合金长杆弹侵彻45钢鉴证靶和约束AD95陶瓷复合靶进行了对比研究。通过数值模拟与实验结合的方法,得到了AD95陶瓷的JH2模型(Johnson—Holmquist ceramic material model)参数;深入分析了钨合金长杆弹侵彻约束AD95陶瓷复合靶侵彻响应过程。

(Jiang D, Li Y C, Yu S J, Deng S C.2010.

Penetation of confined AD95 ceramic composite targets by tungsten long rods

. Explosion and Shock Waves, 30: 91-95).

DOI      URL      [本文引用: 1]      摘要

以侵彻深度(depth of penetration,DOP)实验为基础,利用LSDYNA软件进行数值模拟,对钨合金长杆弹侵彻45钢鉴证靶和约束AD95陶瓷复合靶进行了对比研究。通过数值模拟与实验结合的方法,得到了AD95陶瓷的JH2模型(Johnson—Holmquist ceramic material model)参数;深入分析了钨合金长杆弹侵彻约束AD95陶瓷复合靶侵彻响应过程。
[7] 孔祥振, 方秦, 吴昊, 龚自明. 2017.

长杆弹超高速侵彻半无限靶理论模型的对比分析与讨论

. 振动与冲击, 36: 7

URL      [本文引用: 2]      摘要

分别基于六组典型长杆弹超高速侵彻金属靶体以及三组长杆弹侵蚀侵彻混凝土靶体的实验数据,对经典一维AT模型及其五个改进模型对弹体侵彻深度的预测能力进行了评估,并讨论了靶体等效强度(Rt)变化以及弹体的轴线速度变化。计算结果表明,对于长杆弹高速侵彻金属靶体的分析计算,应首选AW模型,其次为LW模型。而对于混凝土靶体,已有有限的实验数据表明,上述六个模型对于长杆弹侵蚀侵彻混凝土靶体侵彻深度预测均不适用,其主要原因在于Rt不能反映超高速侵彻下混凝土靶体的响应。最后基于分析结果,给出了长杆弹侵蚀侵彻混凝土靶体进一步的研究方向。

(X Kong, Q Fang, H Wu, Z Gong.2017.

Compaision of long rod high velocity penetration models for semi-infinite targets

. Journal of Vibration and Shock, 36: 7).

URL      [本文引用: 2]      摘要

分别基于六组典型长杆弹超高速侵彻金属靶体以及三组长杆弹侵蚀侵彻混凝土靶体的实验数据,对经典一维AT模型及其五个改进模型对弹体侵彻深度的预测能力进行了评估,并讨论了靶体等效强度(Rt)变化以及弹体的轴线速度变化。计算结果表明,对于长杆弹高速侵彻金属靶体的分析计算,应首选AW模型,其次为LW模型。而对于混凝土靶体,已有有限的实验数据表明,上述六个模型对于长杆弹侵蚀侵彻混凝土靶体侵彻深度预测均不适用,其主要原因在于Rt不能反映超高速侵彻下混凝土靶体的响应。最后基于分析结果,给出了长杆弹侵蚀侵彻混凝土靶体进一步的研究方向。
[8] 兰彬. 2008.

长杆弹侵彻半无限靶的数值模拟和理论研究

. [博士论文]. 合肥: 中国科学技术大学

DOI      URL      [本文引用: 1]      摘要

本论文对长杆弹侵彻半无限金属靶板的问题进行了较全面地数值模拟和理论研究。对不同弹靶组合产生的不同侵彻形态,均进行了数值模拟和分析,获得了清晰的侵彻图像、材料变形过程和一些物理量如压力、质点速度等的分布、变化。然后在对数值模拟结果分析的基础上分别建立了理论模型,并成功地以材料性能和初始打击参数来预测侵彻深度和开坑直径。本文的研究和结论对长杆弹动能武器、防护结构的设计和安全评估有重要的理论和实际指导意义,主要内容包括以下几个方面: 用ALE方法和Steinberg本构模型模拟了三类长杆弹侵彻问题。(Ⅰ)对消蚀的钨合金长杆弹侵彻装甲钢靶,得到不同打击速度下均与实验数据吻合的侵彻深度,成功地再现了实验观察到的四个侵彻阶段(瞬态高压段、准定常阶段、惯性扩展阶段和弹性回弹阶段),模拟结果表明弹靶界面附近的材料行为主要由静水压力控制。(Ⅱ)对刚体长杆弹侵彻铝合金靶,使用流固耦合的方法,得到的侵彻深度也与实验数据吻合,发现弹体的横向开坑可分为两阶段-弹体头部开坑和随后靶体材料的惯性运动。(Ⅲ)对变形非消蚀的钢长杆弹侵彻铝合金靶,模拟得到的侵彻深度与实验数据具有相同的变化趋势。撞击初期主要是弹头变粗,其后杆身变粗,变形期间弹尾速度下降较快,侵彻速度较稳定。 建立了长杆弹侵彻半无限靶的理论模型。弹靶组合可根据弹体强度Y_p与靶板静阻力S的关系分为两类: (1)Y_p≤S。弹体只能以消蚀的状态侵彻靶板,并且直接从刚体状态转变为消蚀状态。基于数值模拟分析结果,靶板在高速侵彻下的响应区被划分为流动区、塑性区和弹性区,流动区内材料视为无粘流体,用修正Bernoulli方程描述,塑性区和弹性区的材料行为用空穴膨胀模型描述,从而建立了长杆弹侵彻的新一维模型并给出了界面失效速度(Interface Defeat Velocity)的表达式。模型的预测侵彻深度与实验数据非常吻合。 (2)Y_p>S。根据打击速度的大小,长杆弹可能存在三种状态,即刚性弹、变形非消蚀弹和消蚀弹。针对这三种状态,确定了临界转化条件即刚体速度(V_R)和流体动力学速度(V_H)的确定方法。对刚体侵彻,由之前得到的弹靶界面压力与侵彻速度的关系容易得到弹体受到的阻力;对于变形非消蚀弹侵彻,根据Forrestal和Piekutowski的4340钢长杆弹侵彻半无限6061-T6511铝合金靶实验结果提出了开坑面积随打击速度变化的关系,利用质量和动量守恒定律以及靶板阻力随侵彻速度的变化规律建立了变形非消蚀状态的弹体的u~v关系(其中u、v分别为侵彻速度和弹尾速度),进而根据运动学关系求解了侵彻深度。结果表明:模型预测与实验结果较吻合,体现了相同的变化趋势。 建立了长杆弹侵彻半无限靶的横向开坑模型。对弹体的变形和材料流动引入假定,利用新的一维模型得到的u~v关系和质量、动量、能量三大守恒定律并结合实验观察分别给出了Y_p≤S和Y_p>S的开坑直径计算公式,模型应用于不同弹靶材料,均得到与实验数据一致的预测结果。 研究了夹心长杆弹侵彻半无限靶问题。首先对不同外套-弹芯外径比的夹心长杆弹侵彻进行了数值模拟,模拟结果表明在r_(j0)/r_(c0)(外套外半径与弹芯半径之比)不太大的情形下,夹心长杆弹的u~v关系与去掉外套(或外套与弹芯材料相同)时的均质长杆弹差别很小,可直接用均质长杆弹的u~v关系代替。然后利用三大守恒定律和新的一维模型的u~v关系建立了夹心长杆弹开坑模型,并给出了产生co-erosion状态的临界条件(r_(j0)/r_(c0))_C的计算方法。理论模型较准确地预测了外套为EN24钢的钨合金夹心长杆弹侵彻装甲钢靶的开坑半径,并指出(r_(j0)/r_(c0))_C随打击速度增大而增大,可用减小r_(j0)/r_(c0)和增大打击速度来避免产生bi-erosion状态。

(Lan B.2008.

A combined numerical and theoretical study of long rod penetration into semi-infinite targets

. [PhD Thesis]. Hefei: University of Science and Technology of China).

DOI      URL      [本文引用: 1]      摘要

本论文对长杆弹侵彻半无限金属靶板的问题进行了较全面地数值模拟和理论研究。对不同弹靶组合产生的不同侵彻形态,均进行了数值模拟和分析,获得了清晰的侵彻图像、材料变形过程和一些物理量如压力、质点速度等的分布、变化。然后在对数值模拟结果分析的基础上分别建立了理论模型,并成功地以材料性能和初始打击参数来预测侵彻深度和开坑直径。本文的研究和结论对长杆弹动能武器、防护结构的设计和安全评估有重要的理论和实际指导意义,主要内容包括以下几个方面: 用ALE方法和Steinberg本构模型模拟了三类长杆弹侵彻问题。(Ⅰ)对消蚀的钨合金长杆弹侵彻装甲钢靶,得到不同打击速度下均与实验数据吻合的侵彻深度,成功地再现了实验观察到的四个侵彻阶段(瞬态高压段、准定常阶段、惯性扩展阶段和弹性回弹阶段),模拟结果表明弹靶界面附近的材料行为主要由静水压力控制。(Ⅱ)对刚体长杆弹侵彻铝合金靶,使用流固耦合的方法,得到的侵彻深度也与实验数据吻合,发现弹体的横向开坑可分为两阶段-弹体头部开坑和随后靶体材料的惯性运动。(Ⅲ)对变形非消蚀的钢长杆弹侵彻铝合金靶,模拟得到的侵彻深度与实验数据具有相同的变化趋势。撞击初期主要是弹头变粗,其后杆身变粗,变形期间弹尾速度下降较快,侵彻速度较稳定。 建立了长杆弹侵彻半无限靶的理论模型。弹靶组合可根据弹体强度Y_p与靶板静阻力S的关系分为两类: (1)Y_p≤S。弹体只能以消蚀的状态侵彻靶板,并且直接从刚体状态转变为消蚀状态。基于数值模拟分析结果,靶板在高速侵彻下的响应区被划分为流动区、塑性区和弹性区,流动区内材料视为无粘流体,用修正Bernoulli方程描述,塑性区和弹性区的材料行为用空穴膨胀模型描述,从而建立了长杆弹侵彻的新一维模型并给出了界面失效速度(Interface Defeat Velocity)的表达式。模型的预测侵彻深度与实验数据非常吻合。 (2)Y_p>S。根据打击速度的大小,长杆弹可能存在三种状态,即刚性弹、变形非消蚀弹和消蚀弹。针对这三种状态,确定了临界转化条件即刚体速度(V_R)和流体动力学速度(V_H)的确定方法。对刚体侵彻,由之前得到的弹靶界面压力与侵彻速度的关系容易得到弹体受到的阻力;对于变形非消蚀弹侵彻,根据Forrestal和Piekutowski的4340钢长杆弹侵彻半无限6061-T6511铝合金靶实验结果提出了开坑面积随打击速度变化的关系,利用质量和动量守恒定律以及靶板阻力随侵彻速度的变化规律建立了变形非消蚀状态的弹体的u~v关系(其中u、v分别为侵彻速度和弹尾速度),进而根据运动学关系求解了侵彻深度。结果表明:模型预测与实验结果较吻合,体现了相同的变化趋势。 建立了长杆弹侵彻半无限靶的横向开坑模型。对弹体的变形和材料流动引入假定,利用新的一维模型得到的u~v关系和质量、动量、能量三大守恒定律并结合实验观察分别给出了Y_p≤S和Y_p>S的开坑直径计算公式,模型应用于不同弹靶材料,均得到与实验数据一致的预测结果。 研究了夹心长杆弹侵彻半无限靶问题。首先对不同外套-弹芯外径比的夹心长杆弹侵彻进行了数值模拟,模拟结果表明在r_(j0)/r_(c0)(外套外半径与弹芯半径之比)不太大的情形下,夹心长杆弹的u~v关系与去掉外套(或外套与弹芯材料相同)时的均质长杆弹差别很小,可直接用均质长杆弹的u~v关系代替。然后利用三大守恒定律和新的一维模型的u~v关系建立了夹心长杆弹开坑模型,并给出了产生co-erosion状态的临界条件(r_(j0)/r_(c0))_C的计算方法。理论模型较准确地预测了外套为EN24钢的钨合金夹心长杆弹侵彻装甲钢靶的开坑半径,并指出(r_(j0)/r_(c0))_C随打击速度增大而增大,可用减小r_(j0)/r_(c0)和增大打击速度来避免产生bi-erosion状态。
[9] 兰彬, 文鹤鸣. 2008.

钨合金长杆弹侵彻半无限钢靶的数值模拟及分析

. 高压物理学报, 22: 245-252

DOI      URL      [本文引用: 1]      摘要

利用显式动力有限元程序ANSYS/LS-DYNA,采用ALE方法和Steinberg本构模型,对钨合金长杆弹侵彻半无限厚钢靶进行了数值模拟,给出了侵彻过程4个阶段的完整图像和相关物理量的时程变化曲线,分析了弹、靶的压力分布、质点速度以及材料的流动特性。结果表明:在较大速度范围内,模拟计算的侵彻深度与实验结果吻合得很好;沿侵彻轴线,弹靶交界面附近的材料行为主要由静水压力控制。

(Lan B, Wen H M.2008.

Numerical simulation and analysis of the penetration of tungsten-alloy long rod into semi-infinite armor steel targets

. Chinese Journal of High Pressure Physics, 22: 245-252).

DOI      URL      [本文引用: 1]      摘要

利用显式动力有限元程序ANSYS/LS-DYNA,采用ALE方法和Steinberg本构模型,对钨合金长杆弹侵彻半无限厚钢靶进行了数值模拟,给出了侵彻过程4个阶段的完整图像和相关物理量的时程变化曲线,分析了弹、靶的压力分布、质点速度以及材料的流动特性。结果表明:在较大速度范围内,模拟计算的侵彻深度与实验结果吻合得很好;沿侵彻轴线,弹靶交界面附近的材料行为主要由静水压力控制。
[10] 兰彬, 文鹤鸣. 2009.

半球形弹头钢长杆弹侵彻半无限铝合金靶的数值模拟

. 工程力学, 26: 183-190

URL      [本文引用: 1]      摘要

The numerical simulation of the penetration of a spherical-nosed 4340 Steel Long Rod into Semi-infinite 6061-T6511 Aluminum Targets is performed with ALE method and Steinberg constitutive model using the ANSYS/LS-DYNA finite element code. It transpires that the state of the steel long rod penetrator changes with increasing impact velocity: first it penetrates the aluminum alloy targets as a rigid body, then as a deformable body without mass loss and finally as an erosive body at higher impact velocities, which is in agreement with the experimental observations made by Forrestal et al. It also transpires that for a deforming non-erosive penetrator the head of the penetrator becomes bigger only in the initial phase and followed by the subsequent thickening of the shank during which the velocity of the penetrator tail decreases rapidly whilst the penetration velocity remains relatively steady; that the stresses in the penetration direction at the two ends of the transition zone between the deformed region and undeformed region are close to Hugoinot Elastic Limit and its initial yield stress, respectively.

(Lan B, Wen H M.2009.

A numerical simulation of the penetration of a spherical-nosed 4340 steel long-rod into semi-infinite 6061-T6511 aluminum targets

. Engineering Mechanics, 26: 183-190).

URL      [本文引用: 1]      摘要

The numerical simulation of the penetration of a spherical-nosed 4340 Steel Long Rod into Semi-infinite 6061-T6511 Aluminum Targets is performed with ALE method and Steinberg constitutive model using the ANSYS/LS-DYNA finite element code. It transpires that the state of the steel long rod penetrator changes with increasing impact velocity: first it penetrates the aluminum alloy targets as a rigid body, then as a deformable body without mass loss and finally as an erosive body at higher impact velocities, which is in agreement with the experimental observations made by Forrestal et al. It also transpires that for a deforming non-erosive penetrator the head of the penetrator becomes bigger only in the initial phase and followed by the subsequent thickening of the shank during which the velocity of the penetrator tail decreases rapidly whilst the penetration velocity remains relatively steady; that the stresses in the penetration direction at the two ends of the transition zone between the deformed region and undeformed region are close to Hugoinot Elastic Limit and its initial yield stress, respectively.
[11] 郎林, 陈小伟, 雷劲松. 2011.

长杆和分段杆侵彻的数值模拟

. 爆炸与冲击, 30: 127-134

DOI      URL      [本文引用: 3]      摘要

利用ANSYS/LS-DYNA程序,采用Lagrange方法和Johnson-Cook本构模型,对长径比为5的平头钨合金长杆弹、分段体长径比为1的理想分段杆和带套筒的分段杆侵彻半无限厚钢靶进行了三维数值模拟。给出了侵彻过程中典型时刻的物理图像,并对3种杆的侵彻性能进行了比较。结果表明:分段杆侵彻深度的主要贡献在相Ⅲ惯性扩孔阶段而非连续长杆的相Ⅱ准定常侵彻阶段;分段间隔对侵彻深度的增加有显著影响;套筒的贡献主要在于弹坑直径的增加而对侵深影响微小。

(Lang L, Chen X W, Lei J S.2011.

Numerical simulation on long rod and segmented rods penetration into steel targets

. Explosion and Shock Waves, 30: 127-134).

DOI      URL      [本文引用: 3]      摘要

利用ANSYS/LS-DYNA程序,采用Lagrange方法和Johnson-Cook本构模型,对长径比为5的平头钨合金长杆弹、分段体长径比为1的理想分段杆和带套筒的分段杆侵彻半无限厚钢靶进行了三维数值模拟。给出了侵彻过程中典型时刻的物理图像,并对3种杆的侵彻性能进行了比较。结果表明:分段杆侵彻深度的主要贡献在相Ⅲ惯性扩孔阶段而非连续长杆的相Ⅱ准定常侵彻阶段;分段间隔对侵彻深度的增加有显著影响;套筒的贡献主要在于弹坑直径的增加而对侵深影响微小。
[12] 李继承, 陈小伟. 2011a.

尖锥头长杆弹侵彻的界面击溃分析

. 力学学报, 43: 63-70

DOI      URL      [本文引用: 1]      摘要

在Alekseevski-Tate模型基础上,理论分析了尖锥头长杆弹的界面击溃过程,分别给出在锥头侵蚀阶段和弹身侵蚀阶段的弹体速度下降及质量侵蚀计算公式;随后分析弹体的动能损失,讨论半锥角对弹体动能损失的影响.通过分析小子弹撞击陶瓷/金属复合靶板的例子,验证了该理论的正确性,并对比分析了尖锥头长杆弹与小子弹及平头长杆弹在界面击溃中动能损失之间的差异.

(Li J C, Chen X W.2011a. Theoratical analysis on the interface defeat of a conical-nosed projectile penetration. Chinese Journal of Theoretical and Applied Mechanics, 43: 63-70).

DOI      URL      [本文引用: 1]      摘要

在Alekseevski-Tate模型基础上,理论分析了尖锥头长杆弹的界面击溃过程,分别给出在锥头侵蚀阶段和弹身侵蚀阶段的弹体速度下降及质量侵蚀计算公式;随后分析弹体的动能损失,讨论半锥角对弹体动能损失的影响.通过分析小子弹撞击陶瓷/金属复合靶板的例子,验证了该理论的正确性,并对比分析了尖锥头长杆弹与小子弹及平头长杆弹在界面击溃中动能损失之间的差异.
[13] 李继承, 陈小伟. 2011b.

柱形长杆弹侵彻的界面击溃分析

. 爆炸与冲击, 30: 141-147

DOI      URL      [本文引用: 1]      摘要

在Alekseevski-Tate模型的基础上,分析了柱形长杆弹的界面击溃过程,给出了弹体速度下降及质量侵蚀的计算公式;讨论了弹体速度下降及质量侵蚀对动能损失的影响;特别针对柱形长杆弹在界面击溃过程中弹体速度准定常小量变化的特点,近似给出了弹体速度、弹体质量随时间变化的简化解析表达式,为工程应用提供便利。

(Li J C, Chen X W.2011b. Theoretical analysis on the interface deafeat of a long rod penetration. Explosion and Shock Waves, 30: 141-147).

DOI      URL      [本文引用: 1]      摘要

在Alekseevski-Tate模型的基础上,分析了柱形长杆弹的界面击溃过程,给出了弹体速度下降及质量侵蚀的计算公式;讨论了弹体速度下降及质量侵蚀对动能损失的影响;特别针对柱形长杆弹在界面击溃过程中弹体速度准定常小量变化的特点,近似给出了弹体速度、弹体质量随时间变化的简化解析表达式,为工程应用提供便利。
[14] 李继承, 陈小伟. 2011c.

块体金属玻璃及其复合材料的压缩剪切特性和侵彻/穿甲“自锐”行为

. 力学进展, 41: 480-518

DOI      URL      [本文引用: 1]      摘要

For their excellent mechanical, physical and chemic performance, metallic glasses and their composite materials is becoming as an active research focus now. Especially, metallic glass matrix composite may be employed as the material of kinetic enrgy penetrator for its intense shear banding sensitivity. The present paper introduces the research advance up-to-date on the compressive shear characteristics and self-sharpening behavior of metallic glasses and their composite materials during the high-speed impact. The related experimental research, theoretical analysis and FEM simulations are reviewed, and also some future research proposals are made.

(Li J C, Chen X W.2011c. Compressive-shear behavior and self-sharpening of bulk metallic glass and their composite materials. Advances in Mechanics, 41: 480-518).

DOI      URL      [本文引用: 1]      摘要

For their excellent mechanical, physical and chemic performance, metallic glasses and their composite materials is becoming as an active research focus now. Especially, metallic glass matrix composite may be employed as the material of kinetic enrgy penetrator for its intense shear banding sensitivity. The present paper introduces the research advance up-to-date on the compressive shear characteristics and self-sharpening behavior of metallic glasses and their composite materials during the high-speed impact. The related experimental research, theoretical analysis and FEM simulations are reviewed, and also some future research proposals are made.
[15] 李金柱, 黄风雷, 张连生. 2014.

陶瓷材料抗长杆弹侵彻阻抗研究

. 北京理工大学学报, 34 : 1-4

URL      [本文引用: 3]      摘要

为探讨长杆弹侵彻陶瓷靶中的阻抗与侵彻速度关系,基于长杆弹侵彻半无限靶的修正流体动力学模型(Tate模型)和空腔膨胀理论流体动力学模型,结合文献中已知试验数据,求解了氧化铝和氮化铝陶瓷的Tate模型侵彻阻抗Rt和空腔膨胀模型侵彻阻抗Rc.结果表明在1 500~3 500 m/s速度范围内,氧化铝陶瓷的Rt随速度的增加而缓慢降低,氮化铝的Rt基本为恒值;在3 600~4 500 m/s速度范围内,氮化铝陶瓷的Rt随速度的增加反而增加,可能是侵彻速率超过裂纹传播最终速率所导致;两种陶瓷的Rc都随速度的增加而减小,接近流体动力学极限时Rc值非常小,表明该模型不适合于超高速侵彻.采用平均阻抗计算的侵彻深度结果表明平均阻抗可以用于侵彻深度计算.

(Li J Z, Huang F L, Zhang L S.2014.

Penetration resistance of ceramic materials subjected to projectile's impact

. Transactions of Beijing Institute of Technology, 34: 1-4).

URL      [本文引用: 3]      摘要

为探讨长杆弹侵彻陶瓷靶中的阻抗与侵彻速度关系,基于长杆弹侵彻半无限靶的修正流体动力学模型(Tate模型)和空腔膨胀理论流体动力学模型,结合文献中已知试验数据,求解了氧化铝和氮化铝陶瓷的Tate模型侵彻阻抗Rt和空腔膨胀模型侵彻阻抗Rc.结果表明在1 500~3 500 m/s速度范围内,氧化铝陶瓷的Rt随速度的增加而缓慢降低,氮化铝的Rt基本为恒值;在3 600~4 500 m/s速度范围内,氮化铝陶瓷的Rt随速度的增加反而增加,可能是侵彻速率超过裂纹传播最终速率所导致;两种陶瓷的Rc都随速度的增加而减小,接近流体动力学极限时Rc值非常小,表明该模型不适合于超高速侵彻.采用平均阻抗计算的侵彻深度结果表明平均阻抗可以用于侵彻深度计算.
[16] 李志康, 黄风雷. 2010.

高速长杆弹侵彻半无限混凝土靶的理论分析

. 北京理工大学学报, 30: 10-13

URL      [本文引用: 2]      摘要

为了从理论上确定混凝土材料的靶板阻力,采用三段式线性状态方程和考虑拉伸破坏与剪切饱和的 Mo—hr-Coulomb屈服准则描述混凝土材料,将半无限混凝土靶在高速冲击下的响应分为弹性区、开裂区、孔隙压实区和密实区,建立了混凝土材料的准 静态空腔膨胀理论,确定了靶板阻力,运用A-T模型进行了长杆弹高速侵彻半无限混凝土靶的理论分析.算例结果表明,侵彻深度的理论分析结果与实验结果具有 较好的一致性.

(Li Z K, Huang F L.2010.

High velocity long rod projectile's penetration into semi-infinite concrete targets

. Transactions of Beijing Institute of Technology, 30: 10-13).

URL      [本文引用: 2]      摘要

为了从理论上确定混凝土材料的靶板阻力,采用三段式线性状态方程和考虑拉伸破坏与剪切饱和的 Mo—hr-Coulomb屈服准则描述混凝土材料,将半无限混凝土靶在高速冲击下的响应分为弹性区、开裂区、孔隙压实区和密实区,建立了混凝土材料的准 静态空腔膨胀理论,确定了靶板阻力,运用A-T模型进行了长杆弹高速侵彻半无限混凝土靶的理论分析.算例结果表明,侵彻深度的理论分析结果与实验结果具有 较好的一致性.
[17] 楼建锋. 2012.

侵彻半无限厚靶的理论模型与数值模拟研究

. [博士论文]. 绵阳: 中国工程物理研究院

URL      [本文引用: 1]      摘要

本文针对侵彻半无限厚靶问题,将其划分成刚性弹侵彻、长杆弹高速侵彻、大范围着速的侵彻问题等方面,系统地开展了理论分析和数值模拟研究。内容涉及理论分析模型、数值模拟方法、侵彻性能的影响因素和参数敏感性分析等。本文的研究工作对于侵彻毁伤评估、动能武器研制和防护工程设计,都有重要的理论和实际指导意义。研究内容主要有以下几个方面: (1)系统分析了刚性弹侵彻半无限厚靶的相关理论,包括空腔膨胀理论、速度势和速度场理论,以及主要的半经验、经验公式。分别针对金属材料和混凝土类材料,讨论了常用的侵彻深度计算公式的优缺点和适用性,分析了屈服强度对计算结果的影响,以及弹头形状对侵彻深度的影响。研究表明,弹头形状对侵彻深度有较大的影响。 (2)总结了长杆弹高速侵彻半无限厚靶的理论模型,将6个主要的模型统一写成A-T模型的形式,编制了计算程序,研究了靶板阻力项随侵彻速度和撞击速度的变化关系,讨论了各模型的差异。系统分析了弹靶材料的动态屈服强度、杆弹的长径比对侵彻性能的影响。研究表明,靶的动态屈服强度比长杆弹的动态屈服强度对侵彻深度的影响更明显。 (3)对于大范围着速的侵彻问题,首先,基于对刚性弹到侵蚀弹过渡区间侵彻行为的分析,构造了过渡区靶板阻力的唯象模型和侵彻深度的计算公式,确定了过渡区边界速度的求解方法。其次,在分析三个响应区特征的基础上,构建了三段组合式的理论分析模型,组合模型的预测侵深与试验数据符合较好。 (4)针对钨合金杆高速侵彻半无限厚铝合金靶问题,使用Lagrange方法,开展了数值模拟研究,分析了钨合金杆的材料参数(失效应变、屈服强度和剪切模量)的敏感性,以及弹头形状和长径比对侵深的影响。研究结果表明,失效应变是影响侵彻深度的主要参数,而屈服强度和剪切模量对侵深的影响很小;在较低的撞击速度下,头部形状对侵彻深度的影响较大,而在高着速的情况下,影响很小;以杆长无量纲化的侵彻深度随长径比的增大而降低,表明采用增大长径比提高长杆弹侵彻能力的方式将随着长径比的不断增大,侵彻效率逐渐降低。 另外,对大范围着速的钨杆侵彻铝靶问题,划分成中低速和高速两个区间,选用不同的本构关系,分别建立计算模型进行了数值模拟。在低着速(600m/s)与高着速(800-2000m/s)情况下,计算结果和试验数据较好地符合,同时,过渡区侵彻深度突然大幅下降的现象也有所反映。 (5)讨论了钢筋混凝土靶的建模问题,分析了三种钢筋和混凝土耦合建模方法的优缺点,以及材料失效判据对计算结果的影响。通过数值模拟研究了含筋率和弹着点对钢筋混凝土靶抗侵彻性能的影响。研究表明,钢筋越粗或者钢筋编织越密,即含筋率越高,钢筋混凝土靶板的抗侵彻能力越强,尤其对于动能弹直径大于靶板中钢筋间距的情况;同时,弹着点对动能弹侵彻能力有较大的影响。 针对均匀规则的靶网结构,构造了任意着靶位置的剩余速度或侵彻深度的预估公式。利用这个公式,只需得到三个典型位置动能弹穿靶后的剩余速度或侵彻深度,就可以有效地求解任意着靶位置的剩余速度或侵彻深度。 (6)对于动能弹侵彻多介质组合靶问题,通过数值模拟得到侵彻轨迹、弹体速度、减加速度以及侵彻深度的变化曲线,着重分析了入射倾角和攻角对侵彻毁伤的影响规律。对大倾角斜侵彻问题有了新的认识,弹体在侵彻过程中可能发生反向偏转,深入分析后得到,弹道偏转是由于弹体周围靶板的损伤程度不同引起。

(Lou J F.2012.

Theoretical model and numerical study on penetration into semi-infinite targets

. [PhD Thesis]. Mianyang: China Academy of Engineering Physics).

URL      [本文引用: 1]      摘要

本文针对侵彻半无限厚靶问题,将其划分成刚性弹侵彻、长杆弹高速侵彻、大范围着速的侵彻问题等方面,系统地开展了理论分析和数值模拟研究。内容涉及理论分析模型、数值模拟方法、侵彻性能的影响因素和参数敏感性分析等。本文的研究工作对于侵彻毁伤评估、动能武器研制和防护工程设计,都有重要的理论和实际指导意义。研究内容主要有以下几个方面: (1)系统分析了刚性弹侵彻半无限厚靶的相关理论,包括空腔膨胀理论、速度势和速度场理论,以及主要的半经验、经验公式。分别针对金属材料和混凝土类材料,讨论了常用的侵彻深度计算公式的优缺点和适用性,分析了屈服强度对计算结果的影响,以及弹头形状对侵彻深度的影响。研究表明,弹头形状对侵彻深度有较大的影响。 (2)总结了长杆弹高速侵彻半无限厚靶的理论模型,将6个主要的模型统一写成A-T模型的形式,编制了计算程序,研究了靶板阻力项随侵彻速度和撞击速度的变化关系,讨论了各模型的差异。系统分析了弹靶材料的动态屈服强度、杆弹的长径比对侵彻性能的影响。研究表明,靶的动态屈服强度比长杆弹的动态屈服强度对侵彻深度的影响更明显。 (3)对于大范围着速的侵彻问题,首先,基于对刚性弹到侵蚀弹过渡区间侵彻行为的分析,构造了过渡区靶板阻力的唯象模型和侵彻深度的计算公式,确定了过渡区边界速度的求解方法。其次,在分析三个响应区特征的基础上,构建了三段组合式的理论分析模型,组合模型的预测侵深与试验数据符合较好。 (4)针对钨合金杆高速侵彻半无限厚铝合金靶问题,使用Lagrange方法,开展了数值模拟研究,分析了钨合金杆的材料参数(失效应变、屈服强度和剪切模量)的敏感性,以及弹头形状和长径比对侵深的影响。研究结果表明,失效应变是影响侵彻深度的主要参数,而屈服强度和剪切模量对侵深的影响很小;在较低的撞击速度下,头部形状对侵彻深度的影响较大,而在高着速的情况下,影响很小;以杆长无量纲化的侵彻深度随长径比的增大而降低,表明采用增大长径比提高长杆弹侵彻能力的方式将随着长径比的不断增大,侵彻效率逐渐降低。 另外,对大范围着速的钨杆侵彻铝靶问题,划分成中低速和高速两个区间,选用不同的本构关系,分别建立计算模型进行了数值模拟。在低着速(600m/s)与高着速(800-2000m/s)情况下,计算结果和试验数据较好地符合,同时,过渡区侵彻深度突然大幅下降的现象也有所反映。 (5)讨论了钢筋混凝土靶的建模问题,分析了三种钢筋和混凝土耦合建模方法的优缺点,以及材料失效判据对计算结果的影响。通过数值模拟研究了含筋率和弹着点对钢筋混凝土靶抗侵彻性能的影响。研究表明,钢筋越粗或者钢筋编织越密,即含筋率越高,钢筋混凝土靶板的抗侵彻能力越强,尤其对于动能弹直径大于靶板中钢筋间距的情况;同时,弹着点对动能弹侵彻能力有较大的影响。 针对均匀规则的靶网结构,构造了任意着靶位置的剩余速度或侵彻深度的预估公式。利用这个公式,只需得到三个典型位置动能弹穿靶后的剩余速度或侵彻深度,就可以有效地求解任意着靶位置的剩余速度或侵彻深度。 (6)对于动能弹侵彻多介质组合靶问题,通过数值模拟得到侵彻轨迹、弹体速度、减加速度以及侵彻深度的变化曲线,着重分析了入射倾角和攻角对侵彻毁伤的影响规律。对大倾角斜侵彻问题有了新的认识,弹体在侵彻过程中可能发生反向偏转,深入分析后得到,弹道偏转是由于弹体周围靶板的损伤程度不同引起。
[18] 钱伟长. 1984. 穿甲力学. 北京: 国防工业出版社

[本文引用: 1]     

(Qian W C.1984.Penetration Mechanics. Beijing: National Defense Industry Press).

[本文引用: 1]     

[19] 谈梦婷, 张先锋, 包阔, 伍杨, 吴雪. 2019.

装甲陶瓷的界面击溃效应

. 力学进展, 49: doi: 10.6052/1000-0992-17-015

URL      [本文引用: 1]     

(Tan M T, Zhang F X, Bao K, Wu Y, Wu X.2019.

Interface defeat of ceramic armor

. Advances in Mechanics , 49: doi:10.6052/1000-0992-17-015).

URL      [本文引用: 1]     

[20] 谈梦婷, 张先锋, 葛贤坤, 刘闯, 熊玮. 2017.

长杆弹撞击装甲陶瓷界面击溃/侵彻转变速度理论模型

. 爆炸与冲击, 37: 1093-1100

DOI      URL      [本文引用: 1]      摘要

为预测长杆弹撞击装甲陶瓷界面击溃/侵彻转变过程,采用Hertz接触理论确定靶体内部应力,将其分别应用于陶瓷锥裂纹与翼型裂纹扩展理论。通过比较两种裂纹扩展模型计算得到的界面击溃/侵彻转变速度,提出准确预测界面击溃/侵彻转变速度的理论模型。结果表明:将两种裂纹扩展理论相结合的理论模型可以合理地解释界面击溃/侵彻转变过程,转变速度计算结果与已有实验结果吻合较好。弹体半径较小时,锥裂纹扩展控制界面击溃/侵彻转变过程;弹体半径较大时,翼型裂纹扩展控制界面击溃/侵彻转变过程。

(Tan M T, Zhang F X, Ge X K, Liu C, Xiong W.2017.

Theoretical model of interface defeat/penetration transition velocity of ceramic armor impacted by long-rod projectile

. Explosion and Shock Waves, 37: 1093-1100).

DOI      URL      [本文引用: 1]      摘要

为预测长杆弹撞击装甲陶瓷界面击溃/侵彻转变过程,采用Hertz接触理论确定靶体内部应力,将其分别应用于陶瓷锥裂纹与翼型裂纹扩展理论。通过比较两种裂纹扩展模型计算得到的界面击溃/侵彻转变速度,提出准确预测界面击溃/侵彻转变速度的理论模型。结果表明:将两种裂纹扩展理论相结合的理论模型可以合理地解释界面击溃/侵彻转变过程,转变速度计算结果与已有实验结果吻合较好。弹体半径较小时,锥裂纹扩展控制界面击溃/侵彻转变过程;弹体半径较大时,翼型裂纹扩展控制界面击溃/侵彻转变过程。
[21] 谈梦婷, 张先锋, 何勇, 刘闯, 于溪, 郭磊. 2016.

长杆弹撞击装甲陶瓷的界面击溃效应数值模拟

. 兵工学报, 37: 627-634

DOI      URL      [本文引用: 6]      摘要

利用动力有限元软件AUTODYN模拟了长杆弹撞击装甲陶瓷的界面击溃效应及其影响因素。在验证计算模型、参数及算法可靠的基础上,模拟研究了长杆弹头部形状、盖板、陶瓷预应力等对界面击溃效应的影响规律。结果表明:平头、球形和锥形头部形状长杆弹界面击溃/侵彻转变速度有显著差异;增加盖板及对陶瓷施加预应力均可减小陶瓷的损伤破坏程度,提高陶瓷的界面击溃/侵彻转变速度,提高装甲陶瓷抗弹能力。

(Tan M T, Zhang X F, He Y, Liu C, Yu X, Guo L.2016.

Numerical simulation on interface defeat of ceramic armor impacted by long-rod projectile

. Acta Armamentarii, 37: 627-634).

DOI      URL      [本文引用: 6]      摘要

利用动力有限元软件AUTODYN模拟了长杆弹撞击装甲陶瓷的界面击溃效应及其影响因素。在验证计算模型、参数及算法可靠的基础上,模拟研究了长杆弹头部形状、盖板、陶瓷预应力等对界面击溃效应的影响规律。结果表明:平头、球形和锥形头部形状长杆弹界面击溃/侵彻转变速度有显著差异;增加盖板及对陶瓷施加预应力均可减小陶瓷的损伤破坏程度,提高陶瓷的界面击溃/侵彻转变速度,提高装甲陶瓷抗弹能力。
[22] 王杰, 陈小伟, 韦利明, 雷劲松. 2014.

80%钨纤维增强锆(Zr)基块体金属玻璃复合材料长杆弹侵彻钢靶实验研究

. 实验力学, 29: 279-285

[本文引用: 1]     

(Wang J, Chen X W, Wei L M, Lei J S.2014.

Experimental research on steel target penetration of long rod projectile made of 80% W-fiber/Zr-based BMG

. Experimental Mechanics, 29: 279-285).

[本文引用: 1]     

[23] 魏雪英, 俞茂宏. 2002.

钨杆弹高速侵彻陶瓷靶的理论分析

. 兵工学报, 23: 167-170

DOI      URL      [本文引用: 1]      摘要

ceramics are often used as protective materials against impact damage because of their desir-able properties such as low density, high hardness and compressive strength. Ceramic targets are fragment?ed and comminuted locally by the extreme compressive stress wave occurring at the penetrator-target inter?face when a penetrator impacts the ceramic targets at high velocity. As the penetrator proceeds, a commin?uted zone is finally produced near the tip of the penetrator. The paper considers the influence of this region and derives the target strength term Rt in an A-T model based on the spherically symmetric cavity expan?sion theory. The depth of penetration is calculated using the A-T model when long tungsten rods impact targets at 1.5?4.5km/s. Results of this model are compared with experimental data.

(Wei X Y, Yu M H.2002.

Analysis of tungsten rods on penetrating ceramic targets at high velocity

. Acta Armamentarii, 23: 167-170).

DOI      URL      [本文引用: 1]      摘要

ceramics are often used as protective materials against impact damage because of their desir-able properties such as low density, high hardness and compressive strength. Ceramic targets are fragment?ed and comminuted locally by the extreme compressive stress wave occurring at the penetrator-target inter?face when a penetrator impacts the ceramic targets at high velocity. As the penetrator proceeds, a commin?uted zone is finally produced near the tip of the penetrator. The paper considers the influence of this region and derives the target strength term Rt in an A-T model based on the spherically symmetric cavity expan?sion theory. The depth of penetration is calculated using the A-T model when long tungsten rods impact targets at 1.5?4.5km/s. Results of this model are compared with experimental data.
[24] 徐晨阳, 张先锋, 刘闯, 邓佳杰, 郑应民. 2018.

大着速范围长杆弹侵彻深度变化及其影响因素的数值模拟

. 高压物理学报, 32: 1-9

URL      [本文引用: 2]      摘要

高速/超高速侵彻问题一直是武器设计者和防护工程专家关注的焦点问题之一。随着撞击速度的提高,弹体可能进入流体侵彻阶段,侵彻深度不再随速度的增大单调上升。针对撞击速度增加侵彻深度可能出现增量逆转的现象,开展了大着速范围长杆弹侵彻深度变化的数值模拟研究,分析了弹体硬度、头部形状、弹体材料及靶体材料对侵彻转变点的影响。结果表明:随着长杆弹冲击速度的提升,侵彻深度先上升后下降;同时,弹体硬度提高,到达侵彻转变点对应的撞击速度提高;尖卵形头部弹体到达侵彻转变点的撞击速度比球形头部弹体高;此外,弹靶材料对侵彻深度转变也有较大的影响。

(Xu C Y, Zhang X F, Liu C, Deng J J, Zheng Y M.2018.

Depth of penetration and its influence factors of long rod projectile impacting on semiInfinite target with elevated velocity

. Chinese Journal of High Pressure Physics, 32: 1-9).

URL      [本文引用: 2]      摘要

高速/超高速侵彻问题一直是武器设计者和防护工程专家关注的焦点问题之一。随着撞击速度的提高,弹体可能进入流体侵彻阶段,侵彻深度不再随速度的增大单调上升。针对撞击速度增加侵彻深度可能出现增量逆转的现象,开展了大着速范围长杆弹侵彻深度变化的数值模拟研究,分析了弹体硬度、头部形状、弹体材料及靶体材料对侵彻转变点的影响。结果表明:随着长杆弹冲击速度的提升,侵彻深度先上升后下降;同时,弹体硬度提高,到达侵彻转变点对应的撞击速度提高;尖卵形头部弹体到达侵彻转变点的撞击速度比球形头部弹体高;此外,弹靶材料对侵彻深度转变也有较大的影响。
[25] 翟阳修, 吴昊, 方秦. 2017.

基于A-T模型的长杆弹超高速侵彻陶瓷靶体强度分析

. 振动与冲击, 36: 183-188

DOI      URL      [本文引用: 5]      摘要

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。

(Zhai Y X, Wu H, Fang Q.2017.

Strength analysis of ceramic targets against hypervelocity penetration of long-rod projectiles based on A-T model

. Journal of Vibration and Shock, 36: 183-188).

DOI      URL      [本文引用: 5]      摘要

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。
[26] 张连生, 黄风雷. 2005.

抗弹陶瓷材料抗弹性能的理论表征

. 北京理工大学学报, 25: 651-654

DOI      URL      [本文引用: 1]      摘要

With Tate penetration theory and cavity expansion theory, the kinematic parameters of the long rod penetration and the ceramics differential efficiency factor DEF are expressed as functions of the materials properties. In this way the experimental index of the ballistic performance of armor ceramics is theoretically expressed and the key ceramic properties which have the most significant influences on ballistic performance are mathematically formulated. Calculation shows that this theoretical method can give a good ballistic performance estimate for ceramics against long-rod penetration.

(Zhang L S, Huang F L.2005.

Theoretical characterization of ballistic performance of armor ceramics

. Transactions of Beijing Institute of Technology, 25: 651-654).

DOI      URL      [本文引用: 1]      摘要

With Tate penetration theory and cavity expansion theory, the kinematic parameters of the long rod penetration and the ceramics differential efficiency factor DEF are expressed as functions of the materials properties. In this way the experimental index of the ballistic performance of armor ceramics is theoretically expressed and the key ceramic properties which have the most significant influences on ballistic performance are mathematically formulated. Calculation shows that this theoretical method can give a good ballistic performance estimate for ceramics against long-rod penetration.
[27] Alekseevskii V P.1966.

Penetration of a rod into a target at high velocity. Combustion, Explosion,

and Shock Waves, 2: 63-66.

[本文引用: 6]     

[28] Allen W A, Rogers J W.1961.

Penetration of a rod into a semi-infinite target

. Journal of the Franklin Institute, 272: 275-284.

DOI      URL      [本文引用: 6]      摘要

The penetration of metal rods into semi-infinite metal targets has been investigated experimentally at velocities up to 0.3 cm/ sec. The rods were composed of Au, Pb, Cu, Sn, Al, and Mg; the targets were aluminum. Results are compared with predictions from the hydrodynamic theory of jet penetration. Basic assumptions of the hydrodynamic theory were used to determine an effective yield strength of the target-rod combination. Experimental results indicate that the effective yield strength is relatively independent of the strength of the rod. The hydrodynamic theory of penetration was determined to be generally acceptable except where the density of the jet is much greater than that of the target.A gold jet reveals a new effect of secondary penetration which results in penetration greater than that predicted by theory.
[29] Aly S Y, Li Q M.2008.

Numerical investigation of penetration performance of non-ideal segmented-rod projectiles

. Transactions of Tianjin University, 14: 391-395.

DOI      URL      [本文引用: 2]      摘要

The design of a segmented-rod projectile is often simplified into an ideal one in theoretical analysis for the convenience of modeling of its performance. But the actual performance of non-ideal segmented-rod projectiles over the impact velocity range in practical applications was rarely explored. AUTODYN numerical code is used to investigate the influence of the component design upon the penetration performance of non-ideal segmented-rod projectiles over a wide range of impact velocities, which can be used to guide the optimal design of weaponry segmented-rod projectiles.
[30] Anderson Jr. C E.1987.

An overview of the theory of hydrocodes

. International Journal of Impact Engineering, 5: 33-59.

DOI      URL      [本文引用: 2]      摘要

Hydrocodes are large computer programs that can be used to simulate numerically highly dynamic events, particularly those which include shocks. Lagrangian and Eulerian descriptions are reviewed, and advantages and disadvantages are summarized. The question of how to best represent the continuum equations on a finite computer is answered by summarizing the topics of accuracy and stability. The concept of artificial viscosity is introduced to permit the continuum code to deal with the discontinuities of shocks. Finally, a review of the treatment of materials, i.e., equation of state and constitutive response, including failure, is presented.
[31] Anderson Jr C E.2003.

From fire to ballistics: A historical retrospective

. International Journal of Impact Engineering, 29: 13-67.

DOI      URL      [本文引用: 3]      摘要

This article is the acceptance keynote presentation after receiving the Distinguished Scientist Award from the Hypervelocity Impact Society at HVIS 2000, held in Galveston, TX, November 2000. As dictated by precedence, the article highlights some of the significant events and activities in my career. My technical activities and contributions can be divided into nominally three areas: 1) fire/thermal loading; 2) warhead mechanics; and 3) penetration/armor mechanics. A commonality of the areas is that they all deal with characterizing and understanding the response of materials or structures to intense loads. A summary of my research activities and significant findings are presented. Additionally, a brief history of the formation of the Hypervelocity Impact Society is presented. (C) 2003 Elsevier Ltd. All rights reserved.
[32] Anderson Jr. C E.2017.

Analytical models for penetration mechanics: A review

. International Journal of Impact Engineering, 108: 3-26.

DOI      URL      [本文引用: 1]      摘要

A review of analytical penetration models has been conducted and summarized. Models include the Poncelet equation, hydrodynamic theory, modified hydrodynamic theory, Recht-Ipson, Tate-Alekseevskii, cavity expansion, Ravid-Bodner, Walker-Anderson, and similitude modeling. These models describe, depending upon assumptions, rigid-body penetration, eroding penetration, steady-state and transient penetration, and perforation. Model assumptions are highlighted, and examples are provided of model predictions against experimental data. The manuscript has 30 figures, many of which compare model results to experimental data; 59 reference citations are included.
[33] Anderson Jr. C E, Behner T, Orphal D L, Nicholls A E, Holmquist T J, Wickert M.2008.

Long-rod penetration into intact and pre-damaged SiC ceramic

. Southwest Research Institute, San Antonio, TX, USA.

[本文引用: 3]     

[34] Anderson Jr. C E, Behner T, Holmquist T J, King N L, Orphal D L.2011a.

Interface defeat of long rods impacting oblique silicon carbide

. Southwest Research Institute, San Antonio, TX, USA.

[本文引用: 5]     

[35] Anderson Jr. C E, Chocron S, Bigger R P.2011b.

Time-resolved penetration into glass: Experiments and computations

. International Journal of Impact Engineering, 38: 723-731.

DOI      URL      [本文引用: 2]      摘要

The penetration behavior of tungsten-alloy long-rod penetrators into glass targets is investigated and contrasted at two impact velocities, 1.25 km/s and 1.70 km/s. Penetration depths and residual rod lengths were measured by means of a 600-kV flash X-ray system at different times during penetration. The wavecode CTH was used to simulate numerically the experiments using a Drucker–Prager constitutive model, where the constitutive constants were determined from independent characterization experiments. The numerical results are compared to the experimental data and good agreement is shown.
[36] Anderson Jr. C E, Hohler V, Walker J D, Stilp A J.1999a.

The influence of projectile hardness on ballistic performance

. International Journal of Impact Engineering, 22: 619-632.

DOI      URL      [本文引用: 4]      摘要

http://linkinghub.elsevier.com/retrieve/pii/S0734743X98000694
[37] Anderson Jr. C E, Holmquist T J.2013.

Application of a computational glass model to compute propagation of failure from ballistic impact of borosilicate glass targets

. International Journal of Impact Engineering, 56: 2-11.

DOI      URL      [本文引用: 1]      摘要

Parametric studies were conducted using a recent computational glass model [1] to assess its ability to replicate the rate and extent of damage resulting from ballistic impact of borosilicate glass. Penetration and the position of the failure front were determined as a function of time in experiments using long and short rods at two impact velocities, nominally 1000 m/s and 2100 m/s. Simulations were conducted of the experiments and the results compared to the experiments. Parametric studies examined the effects of very slight changes in the initial impact velocity, time-dependent failure, the inclusion of the third deviatoric stress invariant (J3), mesh resolution, and changes in the strength of intact glass. Results are compared and contrasted, and conclusions drawn on the effect of model parameters in simulating results of impact experiments in different velocity regimes.
[38] Anderson Jr. C E, Morris B L.1992.

The ballistic performance of confined Al$_{2}$O$_{3}$ ceramic tiles

. International Journal of Impact Engineering, 12: 167-187.

DOI      URL      [本文引用: 2]      摘要

The penetration of aluminum oxide tiles inserted into a 4340-steel block that also serves as a emi-infinite steel substrate is investigated for two length-to-diameter projectiles at a nominal impact velocity of 1.5 km/s. The experimental observable is the depth of penetration of the projectile into the backup steel. These data are compared with the total penetration into semi-infinite steel. The data are analysed and displayed as normalized depth of penetration as a function of areal density and tile thickness. Data from Woolsey et al. ( Fifth Annual TACOM Armor Coordinating Conference , Monterey, CA, 1989) are in good agreement with data from this study, and are used to extend the range of tile thicknesses. A methodology, assuming quasi-steady-state penetration, provides an estimate of the penetration resistance R 1 of the ceramic tile; R 1 is then used to estimate the erosion rate and length of projectile eroded as it penetrates the ceramic. A second approach that does not rely as heavily on the assumption of steady-state penetration is also developed and applied to the data to estimate the length of projectile eroded. It is found that the various measures of ceramic performance, for a well-confined target, are relatively constant as tile thickness is varied.
[39] Anderson Jr. C E, Morris B L, Littlefield D L.1992a.

A penetration mechanics database

. Final Report Southwest Research Inst.

URL      [本文引用: 5]      摘要

A penetration mechanics database has been compiled that contains experimental results from a variety of researchers of different nationalities (German, French, English, Canadian, and American), during different decades (the 1960's to the 1990's), and with different purposes or objectives (space debris impact, armor design and evaluation, penetrator design and evaluation, and theoretical verification). The data fall naturally into three subgroupings: (1) penetration into semi-infinite targets; (2) perforation of finite-thickness targets; and (3) penetration from multiple impact (segmented rods). Data collection was primarily limited to experiments conducted against generic type targets, and emphasis was placed on data that would be more relevant to heavy armor issues. This diverse collection of data for metallic targets has been tabulated; data tables include the initial impact conditions, the projectile and target geometries and materials, and the measured response. Information on the materials, e.g., hardness of yield strength, along with impact information such as yaw has been tabulated if available. Graphical displays of the data have been used to summarize the data, and cross-plotting that combines data from different sources has also been provided.
[40] Anderson Jr. C E, Littlefield D L, Walker J D.1993.

Long-rod penetration, target resistance, and hypervelocity impact

. International Journal of Impact Engineering, 14: 1-12.

DOI      URL      [本文引用: 9]     

[41] Anderson Jr. C E, Orphal D L.2003.

Analysis of the terminal phase of penetration

. International Journal of Impact Engineering, 29: 69-80.

DOI      URL      [本文引用: 4]      摘要

ABSTRACT The terminal phase, or Phase 3, of penetration is investigated using numerical simulations. Results of the first set of simulations, for zero-strength tungsten-alloy projectiles into armor steel at velocity of 1.5, 3.0, and 6.0 km/s are reported here. For these simulations, the mechanisms for Phase 3 penetration are limited to the transient deceleration of the eroding projectile and "afterflow," the extension of penetration after the projectile has fully eroded. It is found that for projectile L/D less than or equal to similar to2, there is effectively no steady-state penetration (Phase 2) and penetration is dominated by Phase 3. For projectiles of L/D greater than or equal to 3, steady-state penetration is achieved. For L/D greater than or equal to 3, the deceleration of both the nose and tail of the projectile are essentially independent of LID. For LID greater than or equal to 3, the target penetration associated with Phase 3 is found to increase with impact velocity approximately as P-3/D proportional to V (1.0). "After-flow" as a separate, identifiable mechanism could not be discerned in the results. We therefore question whether the phenomenon of "after-flow," as usually defined, exists; rather, projectile deceleration and crater depth growth are intimately coupled.
[42] Anderson Jr. C E, Orphal D L.2008.

An examination of deviations from hydrodynamic penetration theory

. International Journal of Impact Engineering, 35: 1386-1392.

DOI      URL      [本文引用: 1]      摘要

The hydrodynamic theory of penetration (HTP) was first developed in the U.S. during WWII, and independently and essentially simultaneously in England. Since then the theory has proved very useful in understanding and predicting results of many penetration experiments. The assumptions and limitations of HTP were well stated in the initial paper. The most obvious limitation is that, strictly speaking, HTP only applies to hydrodynamic materials, i.e., both the projectile and the target have no strength. But for nearly all cases of interest, penetration does depend on material strengths, even at quite high velocities. Consequently, effects of projectile and target strength on penetration physics have been studied by many researchers, and modified versions of HTP have been proposed. While material strength is an important reason for deviations from HTP, it is not the only one. Other assumptions underlying HTP are steady-state behavior and incompressibility. In this paper we present new numerical simulation results that examine and quantify deviations from HTP due to compressibility for several material combinations of interest as a function of impact velocity. For these calculations all the materials are modeled as having zero strength. This is done in order to separate effects of compressibility from effects due to material strength. Some discussion of transient effects is also provided.
[43] Anderson Jr. C E, Orphal D L, Behner T, Hohler V, Templeton D W.2006.

Re-examination of the evidence for a failure wave in SiC penetration experiments

. International Journal of Impact Engineering, 33: 24-34.

DOI      URL      [本文引用: 1]      摘要

Previous work suggested the possibility that the effects of a failure wave, evidenced through a change in the slope of the penetration velocity vs. impact velocity ( u– v p) curve resulting from an increase in target penetration resistance, could be observed in penetration experiments of SiC. However, the previous work had to combine two different sets of experimental data, one using long tungsten rods and the other copper shaped-charge jets. A new set of experiments was conducted to address the uncertainties associated with combining the two disparate data sets. Analysis of the new experiments showed no evidence of a distinct change in the slope of the u– v p response of SiC, up to an impact velocity of 6.2 km/s. We re-examine the original data and analysis in light of the new experiments to understand the origins of the original misinterpretation.
[44] Anderson Jr. C E, Orphal D L, Behner T, Templeton D W.2009.

Failure and penetration response of borosilicate glass during short-rod impact

. International Journal of Impact Engineering, 36: 789-798.

DOI      URL      [本文引用: 1]      摘要

In Anderson Jr CE, Orphal DL, Behner T, Templeton, DW [Failure and penetration response of borosilicate glass during short-rod impact. Int J Impact Eng 2009, doi:10.1016/ j.ijimpeng.2008.12.002.] it was demonstrated that the failure front (FF) produced by the penetration of a borosilicate glass target by a gold rod ceased to propagate a short time after the rod was fully eroded. This strongly suggests that progression of the FF is not described by a wave equation. Here it is shown that propagation of the FF is reinitiated if a second co-axial rod, spaced a distance from the first, impacts the glass at the bottom of the penetration channel. The experiments were performed in reverse ballistic mode with two short rods spaced apart. In some experiments both rods were gold; in other experiments, one rod was copper and the other gold. FF propagation was measured using high-speed photography; rod penetration was measured using multiple, independent flash X-rays. Much of the observed phenomenology can be modeled assuming that the rod, either first or second, “communicates” with the FF at a speed corresponding to the bulk sound speed of the undamaged glass.
[45] Anderson Jr. C E, Orphal D L, Franzen R R, Walker J D.1999b.

On the hydrodynamic approximation for long-rod penetration

. International Journal of Impact Engineering, 22: 23-43.

DOI      URL      [本文引用: 1]      摘要

Steady-state hydrodynamic theory, or variations thereof, has been applied to long-rod penetration since the 1940s. It is generally believed that projectile strength is of little consequence at high velocities, and that hydrodynamic theory is applicable to long-rod penetration when penetration pressures are much greater than the target flow stress. Substantiating this belief is the observation that at approximately 2.5 km/s, for tungsten alloy projectiles into armor steel, normalized penetration (P/L) nominally saturates to the classical hydrodynamic limit of the square root of the ratio of the projectile to target densities. Experimental data herein, however, show penetration velocities and instantaneous penetration efficiencies fall below that expected from hydrodynamic theory, even at impact velocities as high as 4.0 km/s. Numerical simulations, using appropriate strength values, are in excellent agreement with the experimental data. Parametric studies demonstrate that both projectile and target strength have a measurable effect even at such high impact velocities.
[46] Anderson Jr. C E, Riegel Iii J J P.2015.

A penetration model for metallic targets based on experimental data

. International Journal of Impact Engineering, 80: 24-35.

DOI      URL      [本文引用: 2]      摘要

61Semi-infinite penetration data are used to predict finite-thickness target effects.61A procedure is developed to estimate ballistic limit velocity and/or ballistic limit thickness.61Similitude analysis extends the database to other materials.61Residual projectile velocity and length are estimated for overmatched targets.61Algorithms are provided to adjust for projectile aspect ratio and size effects.
[47] Anderson Jr. C E, Royal-Timmons S A.1997.

Ballistic performance of confined 99.5%-Al$_{2}$O$_{3}$ ceramic tiles

. International Journal of Impact Engineering, 19: 703-713.

DOI      URL      [本文引用: 4]     

[48] Anderson Jr. C E, Walker J D.1991.

An examination of long-rod penetration

. International Journal of Impact Engineering, 11: 481-501.

DOI      URL      [本文引用: 9]      摘要

The one-dimensional modified Bernoulli theory of Tate [ J. Mech. Phys. Solids 15 , 287 399 (1967)] is often used to examine long-rod penetration into semi-infinite targets. The theory is summarized and the origins of the target resistance term examined. Numerical simulations were performed of a tungsten-alloy, long-rod projectile into a semi-infinite hardened steel target at three impact velocities sufficiently high to result in projectile erosion. The constitutive responses of the target and projectile were varied parametrically to assess the effects of strain hardening, strain-rate hardening, and thermal softening on penetration response. The results of one of the numerical simulations were selected to compare and contrast in detail with the predictions of the Tate model.
[49] Anderson Jr. C E, Walker J D.2005.

An analytical model for dwell and interface defeat

. International Journal of Impact Engineering, 31: 1119-1132.

DOI      URL      [本文引用: 3]      摘要

An analytical model that captures the essential mechanics of dwell and interface defeat—the phenomenon where an impacting projectile flows radially outward (erodes) along the surface of the target (usually ceramic) with no significant penetration—is presented. During dwell, the projectile loses kinetic energy due to mass loss and deceleration. It is shown that model predictions are in very good agreement with experimental data.
[50] Anderson Jr. C E, Walker J D, Bless S J, Partom Y.1996.

On the L/D effect for long-rod penetrators

. International Journal of Impact Engineering, 18: 247-264.

DOI      URL      [本文引用: 8]      摘要

A common measure of penetration efficiency is given by the depth of penetration P into a semi-infinite target normalized by the original length of the projectile L. It has been known for over 30 years that P/L depends upon the aspect ratio LID for projectiles with relatively small aspect ratios, e.g. 1 ≤ L/D ≤ 10. This influence of L/D on penetration is referred to as the LID effect. Although observed, the LID effect for large aspect ratio rods is not as well documented. Further, published penetration equations have not included the LID effect for high aspect ratio rods. We have compiled a large quantity of experimental data that permits the quantification of the L/D effect for projectiles with aspect ratios of 10 ≤ L/D ≤ 30. Numerical simulations reproduce the observed experimental behavior ; thus, no new physics is required to explain the phenomenon. The numerical simulations allow investigation of the fundamental mechanics leading to a decrease in penetration efficiency with increasing aspect ratio.
[51] Anderson Jr. C E, Walker J D, Bless S J, Sharron T R.1995.

On the velocity dependence of the $L/D$ effect for long-rod penetrators

. International Journal of Impact Engineering, 17: 13-24.

DOI      URL      [本文引用: 7]      摘要

At ordnance velocities (1.0 – 1.9 km/s), there is a pronounced decrease in penetration efficiency, as measured by P / L , when projectiles of larger L / D are used. The influence of L / D on penetration is referred to as the L / D effect d. We numerically examine the L / D effect at higher velocities, from 2.0 km/s to 4.5 km/s. It is found that as the velocity increases, there is a change in mechanism for the L / D effect. At ordnance velocities the L / D effect is mostly due to the decay in penetration velocity during the “steady-state” region of penetration. At higher velocities, the steady-state region of penetration shows no L / D dependence, and the L / D effect is due primarily to the penetration of the residual (non-eroding) rod at the end of the penetration event. This change in mechanism is related to the change in slope of the penetration-versus-impact velocity “S-shaped” curve for eroding projectiles.
[52] Anderson Jr. C E, Walker J D, Hauver G E.1992b.

Target resistance for long-rod penetration into semi-infinite targets

. Nuclear Engineering & Design, 138: 93-104.

DOI      URL      [本文引用: 8]      摘要

An important parameter in the one-dimensional modified-Bernoulli penetration theory of Tate is the target resistance R t . In the model, it is assumed that R t remains constant during the total penetration event. In this paper, a parametric study using the Tate model is used to show that the total depth of penetration is sensitive to the value of R 1 , Time-resolved depth-of-penetration experiments and numerical simulations are used to examine R t as a function of penetration depth for long-rod tungsten-alloy projectiles impacting semi-infinite targets of S-7 steel and a titanium alloy. It is found in these studies that R t changes considerably during penetration and that the values which are used in predicting penetration performance must be considered to be an average value over the entire penetration profile.
[53] Andersson O, Lundberg P, Renström R.2007.

Influence of confinement on the transition velocity of silicon carbide//Proceedings of the 23rd international symposium on ballistics,

Tarragona, Spain: 16-20.

[本文引用: 6]     

[54] Aydelotte B, Schuster B.2015.

Impact and penetration of SiC: The role of rod strength in the transition from dwell to penetration

. Procedia Engineering, 103: 19-26.

DOI      URL      摘要

The phenomenon of dwell during projectile impact on ceramics has been an active area of research for several decades. Dwell in confined ceramics has received much attention, particularly the role of cover plates and their influence over the dwell to penetration transition. Dwell during long rod impact on unconfined ceramics has received relatively less attention. The present work will compare and contrast the results of two series of long rod impacts on hot pressed silicon carbide targets. One series utilized gold wire rods. The other series utilized rods fabricated from tungsten carbide with 10% cobalt matrix. A novel ten-flash X-ray system captured spatially resolved images of the penetration events. The experimental results are compared with simulations and predictions from the Alekseevskii-Tate equation to explore the role of shock pressure, the effects of the strength of the rod material in dwell to penetration transition behavior, and the behavior of defects within silicon carbide.
[55] Behner T, Anderson Jr. C E, Holmquist T J, Wickert M, Templeton D W.2008.

Interface defeat for unconfined SiC ceramics//Proceedings of the 24th international symposium on ballistics,

New Orleans: 35-42.

[本文引用: 3]     

[56] Behner T, Anderson Jr. C E, Holmquist T J, Orphal D L, Wickert M, Templeton D W.2011.

Penetration dynamics and interface defeat capability of silicon carbide against long Rod impact

. International Journal of Impact Engineering, 38: 419-425.

DOI      URL      [本文引用: 5]      摘要

To determine the behavior of silicon carbide (SiC) against long rod impact a detailed study with experiments in the velocity range from 0.8 to 3 km/s at normal impact conditions was performed in recent years. Interest ranged from penetration performance of intact and pre-damaged SiC to interface defeat capability of SiC. Together with impact data in the hypervelocity regime this paper provides a comprehensive overview of the penetration dynamics of SiC over a wide velocity range and during different phases of the penetration process.
[57] Behner T, Anderson Jr. C E, Orphal D L, Hohler V, Moll M, Templeton D W.2008.

Penetration and failure of lead and borosilicate glass against rod impact

. International Journal of Impact Engineering, 35: 447-456.

DOI      URL      [本文引用: 4]      摘要

This paper presents the experimental design and results for gold rod impact on DEDF (5.19 g/cm 3) and Borofloat (2.2 g/cm 3) glass by visualizing simultaneously failure propagation in the glass with a high-speed camera and rod penetration with flash radiography. At a given impact velocity, the velocity of the failure front is significantly higher during early penetration than during steady-state penetration of the rod. For equal pressures but different stress states, the failure front velocities determined from Taylor tests or planar-impact tests are greater than those observed during steady-state rod penetration. The ratio of average failure front velocity to rod penetration velocity decreases with increasing impact velocity ( v p) in the range of v p=0.4 2.8 km/s. As a consequence, the distance between the rod tip and the failure front is reduced with increasing v p. The Tate term R T increases with impact velocity.
[58] Behner T, Heine A, Wickert M.2013.

Protective properties of finite-extension ceramic targets against steel and copper projectiles//Proceedings of the 27th International Symposium on Ballistics, Freiburg, Germany

.

[本文引用: 1]     

[59] Behner T, Heine A, Wickert M.2016.

Dwell and penetration of tungsten heavy alloy long-rod penetrators impacting unconfined finite-thickness silicon carbide ceramic targets

. International Journal of Impact Engineering, 95: 54-60.

DOI      URL      [本文引用: 2]      摘要

Impact experiments with a tungsten heavy alloy long rod projectile against silicon carbide tiles were performed to study the transition from dwell to penetration and to compare against earlier investigations which focused either on small scale semi-infinite set-ups or on finite thickness set-ups with confinement. A depth-of-penetration configuration consisting of a ceramic tile and an extended steel backing was used to assess the impact response of the unconfined finite-thickness ceramic. The ceramic tile was either bare or had a cover plate attached to the front. The cover plate thickness has been varied and gives best results for a thickness of about half the projectile diameter used in the experiments. For the bare ceramic, a long dwell phase can be maintained up to impact velocities of around 900 /s. For the buffered ceramic, partial dwell can be achieved up to around 1700 /s. The results corroborate those of earlier investigations mentioned above. More importantly, the present results show that it is possible to substantially erode a heavy alloy long-rod penetrator at the surface of a finite thickness ceramic element without lateral confinement in direct impact experiments even at high impact velocities.
[60] Behner T, Orphal D L, Hohler V, Anderson Jr. C E, Mason R L, Templeton D W.2006.

Hypervelocity penetration of gold rods into SiC-N for impact velocities from 2.0 to 6.2km/s

. International Journal of Impact Engineering, 33: 68-79.

DOI      URL      [本文引用: 1]      摘要

This paper presents the experimental design and results of an advanced set of reverse ballistic experiments with long gold rods, impacting SiC-N ceramics at impact velocities from 2.0 to 6.2 km/s. Important issues for these experiments were the high accuracy and position requirements necessary to detect a possible failure wave or failure kinetics in SiC-ceramics as might be evidenced by a change in the slope of the penetration velocity–impact velocity curve. New and sophisticated evaluation methods were developed for this purpose and produced very reliable results. Analyses of the experimental results show clearly that there is no change in the slope of the penetration velocity–impact velocity curve, contrary to that inferred from previous data and analysis.
[61] Belyakov L V, Vitman F F, Zlatin N A.1963.

Collision of deformable bodies and its modeling

. Soviet Physics-Technical Physics, 8: 736-739.

URL      [本文引用: 1]     

[62] Birkhoff G, Macdougall D P, Pugh E M, Taylor S G.1948.

Explosives with Lined Cavities

. Journal of Applied Physics, 19: 563-582.

DOI      URL      [本文引用: 1]     

[63] Bjerke T W, Silsby G F, Scheffler D R, Mudd R M.1992.

Yawed long-rod armor penetration

. International Journal of Impact Engineering, 12: 281-292.

DOI      URL      [本文引用: 2]      摘要

The terminal ballistic behavior of ductile tungsten alloy long-rod penetrators is examined as impact yaw is increased from values of approximately zero to those which cause penetration performance to significantly decrease. The impact signatures remaining in the target crater from high yaw impacts are examined and used to identify the physical mechanisms which cause penetrator performance to degrade. A threshold limit of penetrator yaw beyond which penetration performance decreases is derived. An empirically based model which quantifies the decrease in penetration due to yaw once this threshold limit is exceeded is presented for impacts with normal incidence semi-infinite RHA targets. The results from a computational effort using the HULL code to simulate high yaw impacts are presented and compared with the empirical penetration degradation model.
[64] Bless S J, Barber J P, Bertke R S, Swift H F.1978.

Penetration mechanics of yawed rods

. International Journal of Engineering Science, 16: 829-834.

DOI      URL      [本文引用: 2]      摘要

The penetration of rod projectiles is a function of impact yaw. Armor steel targets were struck at 0° obliquity by long steel rods at ~2.15 km/s and various angles of yaw. Crater dimensions varied systematically with yaw angle. Trenching behavior was observed for yaw angles exceeding about 30°. Analysis indicates that the rods collapsed into the targets with no significant rotation, and that penetration chiefly depends on the parameters D and D sin θ (where D is rod diameter and θ is yaw angle).
[65] Bless S J, Rosenberg Z, Yoon B.1987.

Hypervelocity penetration of ceramics

. International Journal of Impact Engineering, 5: 165-171.

DOI      URL      [本文引用: 1]      摘要

The penetration resistance of alumina was found to decrease with velocity for armor-piercing bullets. However, it was relatively independent of velocity for rods and fragment-simulating projectiles. These results are explained in terms of compressive yielding caused by high velocity pointed projectiles.
[66] Bukharev Y I, Zhukov V I.1995.

Model of the penetration of a metal barrier by a rod projectile with an angle of attack. Combustion, Explosion,

and Shock Waves, 31: 362-367.

DOI      URL      [本文引用: 3]      摘要

A relatively simple dynamic model is proposed for calculating parameters characterizing the penetration of a barrier by a rod projectile with an angle of attack. Together with the factors examined in the case of axisymmetric penetration within the framework of the well-known Alekseevskii-Tate scheme, the model considers the action of transverse forces and rotation of the rod. Calculations of the penetration of steel barriers by tungsten projectiles with a relative length of 12.8–17.4 at collision velocities of 1800–2100 m/sec along a normal to the surface showed good agreement with experimental data for angles of attack from 0 to 68°.
[67] Burkins M S, Paige J I, Hansen J S.1996.

A ballistic evaluation of Ti-6Al-4v vs

. long rod penetrators. Army Research Laboratory Report ARL-TR-1146.

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[68] Charters A C, Menna T L, Piekutowski A J.1990.

Penetration dynamics of rods from direct ballistic tests of advanced armor components at 2-3km/s

. International Journal of Impact Engineering, 10: 93-106.

DOI      URL      [本文引用: 5]      摘要

The penetration of semi-infinite steel and spaced-plate armors by continuous and segmented rods has been analyzed and measured by direct ballistic tests, hydrocode calculations, and hydrodynamic models at velocities from 2 to 4 km/s. An empirical equation of rod penetration in semi-infinite steel was formulated from hydrodynamic models of rod impact. Penetrations predicted by the equation agreed well with measured values. Increasing the spacing between segments from one to two diameters increased the penetration significantly ( 20%). Structures to support and align the segments can either increase or decrease the penetration, depending on their design. The relative penetrations of continuous and segmented rods depend on the parameters selected for the comparison: the segmented rod having greater penetration for equal mass and diameter and vice versa for equal mass and length. Tests of segmented rods penetrating spaced-plate armor showed that the armor is defeated by the front segment (or segments) punching a hole in the front plate (or plates) that allows the remaining segmented rod through intact to attack the main armor.
[69] Chen X W, Li Q M.2002.

Deep penetration of a non-deformable projectile with different geometrical characteristics

. International Journal of Impact Engineering, 27: 619-637.

DOI      URL      [本文引用: 2]      摘要

A general non-dimensional formula based on the dynamic cavity-expansion model is proposed to predict penetration depth into several mediums subjected to a normal impact of a non-deformable projectile. The proposed formula depends on two dimensionless numbers and shows good agreement with penetration tests on metal, concrete and soil for a range of nose shapes and impact velocities. The validity of the formula requires that the penetration depth is larger than the projectile diameter and the projectile nose length while projectile remains rigid without noticeable deformation and damage.
[70] Chen X W, Li Q M.2004.

Transition from Nondeformable Projectile Penetration to Semihydrodynamic Penetration

. Journal of Engineering Mechanics, 130: 123-127.

DOI      URL      [本文引用: 2]     

[71] Chen X W, Li X L, Huang F L, Wu H J, Chen Y Z.2008.

Damping function in the penetration/perforation struck by rigid projectiles

. International Journal of Impact Engineering, 35: 1314-1325.

DOI      URL      [本文引用: 1]      摘要

The present paper defines a third dimensionless parameter, i.e., the damping function , besides the impact function and geometry function of projectile introduced previously, in the penetration/perforation dynamics of a rigid projectile. It only depends on the interaction of projectile and target materials and is independent of projectile geometry. A general penetration resistance, which contains the terms of viscous effect and dummy mass of projectile induced by the deceleration effect, is adopted in the formulation. Dimensionless formula of depth of penetration (DOP) is conducted with only three parameters , and for general convex shapes of various rigid projectiles. Different geometry parameters are also presented for some common shapes of projectiles. With accounting for viscous effect and dummy mass of a projectile, the normal perforations of thick metallic plates struck by sharp-nosed rigid projectiles are further studied and only , and as well as the dimensionless target thickness dominate in perforation. The influence of damping function on penetration/perforation has been discussed in detail. Theoretical predictions of penetration and perforation in the present manuscript show good agreement with the individual published test data of different projectiles and impact velocities as well as different targets.
[72] Chen X W, Wei L M, Li J C.2015.

Experimental research on the long rod penetration of tungsten-fiber/Zr-based metallic glass matrix composite into Q235 steel target

. International Journal of Impact Engineering, 79: 102-116.

DOI      URL      [本文引用: 2]      摘要

61Penetration tests of WF/Zr-MG composite and WHA long rods are conducted.61Failure modes of WF/Zr-MG composite and WHA are identified systemically.61The “self-sharpening” behavior of composite rod and its mechanism are investigated.61Impact velocity range which is favorable for the “self-sharpening” is suggested.61Comparative analysis between the composite rod and the WHA rod is conducted.
[73] Chocron S, Anderson Jr. C E, Walker J D, Ravid M.2003.

A unified model for long-rod penetration in multiple metallic plates

. International Journal of Impact Engineering, 28: 391-411.

DOI      URL      [本文引用: 1]      摘要

The Walker–Anderson and Ravid–Bodner analytical models for penetration of projectiles in metallic plates are well known in the ballistics community. The Walker–Anderson model uses the centerline momentum balance in the projectile and target to calculate the penetration history into a semi-infinite medium, while the Ravid–Bodner model uses the upper bound theorem of plasticity theory modified to include dynamic effects. The Ravid–Bodner model also includes a rich selection of failure modes suitable for finite-thick metallic targets. In this paper a blended model is presented: momentum balance is used to calculate the semi-infinite portion penetration (before the back of the target plate begins to flow), and the Ravid–Bodner failure modes are used to determine projectile perforation. In addition, the model has been extended to handle multiple plate impact. Numerical simulations show that after target failure the projectile still continues to erode for some microseconds. This time has been estimated and incorporated into the model. Examples are presented for long-rod projectiles against thick and spaced-plate targets backed by a witness pack that is separated from the main target element(s) by an air gap. Agreement with results from numerical simulations is quite good.
[74] Christman D R, Gehring J W.1966.

Analysis of High-Velocity Projectile Penetration Mechanics

. Journal of Applied Physics, 37: 1579-1587.

DOI      URL      [本文引用: 8]     

[75] Cuadros J H.1990.

Monolithic and segmented projectile penetration experiments in the 2 to 4 kilometers per second impact velocity regime

. International Journal of Impact Engineering, 10: 147-157.

DOI      URL      [本文引用: 1]      摘要

A series of experiments was performed to evaluate the performance of projectiles impacting targets at velocities two to three times larger than conventional ordnance velocities. The results were positive, where low L/D ratio projectiles exceeded the theoretical hydrodynamic limit of penetration for the given projectile-target combination. High L/D ratio projectiles did not appreciably exceed the limit. A second set of experiments was devised to test the hypothesis that a segmented projectile, - consisting of a series of low L/D projectiles, assembled in a long rod configuration, - could penetrate deeper into the target than a monolithic projectile of equivalent mass. The results were again positive, with a gain of about 10% shown in some cases. The balance of the experiments was devoted to developing a set of design rules and to exploring variations in the configuration and materials.
[76] Deshpande V S, Evans A G.2008.

Inelastic deformation and energy dissipation in ceramics: A mechanism-based constitutive model

. Journal of the Mechanics and Physics of Solids, 56: 3077-3100.

DOI      URL      [本文引用: 1]      摘要

A mechanism-based constitutive model is presented for the inelastic deformation and fracture of ceramics. The model comprises four essential features: (i) micro-crack extension rates based on stress-intensity calculations and a crack growth law, (ii) the effect of the crack density on the stiffness, inclusive of crack closure, (iii) plasticity at high confining pressures, and (iv) initial flaws that scale with the grain size. Predictions of stress/strain responses for a range of stress states demonstrate that the model captures the transition from deformation by micro-cracking at low triaxiality to plastic slip at high triaxialities. Moreover, natural outcomes of the model include dilation (or bulking) upon micro-cracking, as well as the increase in the shear strength of the damaged ceramic with increasing triaxiality. Cavity expansion calculations are used to extract some key physics relevant to penetration. Three domains have been identified: (i) quasi-static, where the ceramic fails due to the outward propagation of a compression damage front, (ii) intermediate velocity, where an outward propagating compression damage front is accompanied by an inward propagating tensile (or spallation) front caused by the reflection of the elastic wave from the outer surface and (iii) high velocity, wherein plastic deformation initiates at the inner surface of the shell followed by spalling within a tensile damage front when the elastic wave reflects from the outer surface. Consistent with experimental observations, the cavity pressure is sensitive to the grain size under quasi-static conditions but relatively insensitive under dynamic loadings.
[77] Eichelberger R J.1956.

Experimental test of the theory of penetration by metallic jets

. Journal of Applied Physics, 27: 63-68.

DOI      URL      [本文引用: 2]      摘要

Experimental measurements of jet velocity and of penetration velocity as functions of depth of penetration are described for lined cavity charges fired into several types of target material and under a variety of experimental conditions. The results show that the hydrodynamic theory of penetration of Pugh and of Hill, Mott, and Pack describes very accurately the early stages of the penetration process. Strength of the target becomes an appreciable factor in the later stages, however. A simple modification of the theory is described which appears to account adequately for these strength effects. Some alterations in ideas concerning the mechanism of penetration by the jet after fracture are also described.
[78] Eichelberger R J, Gehring J W.1962.

Effects of meteoroid impacts on space vehicles

. ARS Journal, 32: 1583-1591.

DOI      URL      [本文引用: 1]      摘要

The mechanism of crater formation due to hypervelocity impact is described, using a variety of experimental observations and theory as a basis. The currently accepted empirical correlations are also presented. The evidence is considered in the light of the problem of meteoroid impacts upon space vehicles, and such generalized predictions as are possible at the present state of the art are erived. (Author)
[79] Forrestal M J, Altman B S, Cargile J D, Hanchak S J.1994.

An empirical equation for penetration depth of ogive-nose projectiles into concrete targets

. International Journal of Impact Engineering, 15: 395-405.

DOI      URL      [本文引用: 1]      摘要

We conducted depth of penetration experiments with ogive-nose projectiles concrete targets with unconfined compressive strengths of nominally 14 MPa (2 ksi), 35 MPa (5 ksi), and 97 MPa (14 ksi). From our data and the data presented by Canfield and Clator [ J. A. Canfield and I. G. Clator , Development of a scaling law and techniques to investigate penetration in concrete . NWL Report No. 2057, U.S. Naval Weapons Laboratory, Dahlgren, VA (1966) ] [1], we developed an empirical equation for penetration depth of ogive-nose projectiles penetrating concrete targets at normal impact. Our penetration equation contains a single, dimensionless empirical constant that depends only on the unconfined compressive strength of the target. We determine the empirical constant from penetration depth versus striking velocity data with six sets of penetration data for striking velocities between 250 and 800 m/s. Predictions are in good agreement with all six data sets.
[80] Forrestal M J, Frew D J, Hanchak S J, Brar N S.1996.

Penetration of grout and concrete targets with ogive-nose steel projectiles

. International Journal of Impact Engineering, 18: 465-476.

DOI      URL      [本文引用: 1]      摘要

We conducted depth of penetration experiments into grout and concrete targets with ogive-nose steel projectiles. Powder guns launched 0.064 kg, 12.9 mm diameter projectiles into grout targets with unconfined compressive strengths of 13.5 M Pa (2.0 ksi) and 21.6 MPa (3.1 ksi). For the concrete targets, powder guns launched projectiles with length-to-diameter ratios of 10; a 0.48 kg, 20.3 mm diameter rod, and a 1.60 kg, 30.5 mm diameter rod. Concrete targets had unconfined compressive strength of 62.8 M Pa (9.1 ksi) for the 0.48 kg rods and unconfined compressive strength of 51.0 MPa (7.4 ksi) for the 1.60 kg rods. For these experiments, penetration depth increased as striking velocity increased until nose erosion became excessive. Thus, we determined experimentally the striking velocities corresponding to maximum penetration depths. Predictions from a previously published model are in good agreement with data until nose erosion becomes excessive.
[81] Forrestal M J, J. Piekutowski A.2000.

Penetration experiments with 6061-T6511 aluminum targets and spherical-nose steel projectiles at striking velocities between 0.5 and 3.0km/s

. International Journal of Impact Engineering, 24: 57-67.

DOI      URL      [本文引用: 2]      摘要

We conducted depth of penetration experiments with 7.11-mm-diameter, 74.7-mm-long, spherical-nose, 4340 steel projectiles launched into 250-mm-diameter, 6061-T6511 aluminum targets. A powder gun and two-stage, light-gas guns launched the 0.023 kg projectiles at striking velocities between 0.5 and 3.0 km/s. Post-test radiographs of the targets showed three response regions as striking velocities increased: (1) the projectiles had slight bulges near the nose and some shank bending, (2) the projectiles had large bulges and kinked shanks, and (3) the projectiles eroded and lost mass. For the first response region, penetration depth increased as striking velocity increased. However, when the second region was reached, there was a dramatic reduction in penetration depth. For the third response region penetration depth increased with increasing striking velocity. To show the effect of projectile strength, we compared depth-of-penetration as a function of striking velocity for spherical-nose rods with average Rockwell hardnesses of 36.6, 39.5, and 46.2. To show the effect of nose shape, we compared penetration data for the spherical-nose projectiles with previously published data for ogive-nose projectiles.
[82] Forrestal M J, Longcope D B.1990.

Target strength of ceramic materials for high-velocity penetration

. Journal of Applied Physics, 67: 3669-3672.

DOI      URL      [本文引用: 3]      摘要

We derived equations for the target‐strength term used in the modified hydrodynamic model that describes long rod penetration into ceramic targets. Since ceramics have tensile strengths that are usually an order of magnitude lower than their compressive strength, this model allows for tensile cracking. In addition, our model includes the effect of pressure‐dependent shear strength.
[83] Forrestal M J, Piekutowski A J, Luk V K.1988.

Long-rod penetration into simulated geological targets at an impact velocity of 3.0km/s. Military Technology Weaponry &

National Defense.

[本文引用: 2]     

[84] Franzen R R, Orphal D L, Anderson Jr. C E.1997.

The influence of experimental design on depth-of-penetration (DOP) test results and derived ballistic efficiencies

. International Journal of Impact Engineering, 19: 727-737.

DOI      URL      [本文引用: 3]      摘要

Abstract Experimental data for ceramic armor materials from two test methods, small-scale reverse ballistic tests and depth-of-penetration (DOP) tests, are reviewed and compared. Results from reverse ballistic tests can be used to estimate the length of rod erosion in the ceramic tiles of DOP tests. The outcome of a given DOP test can then be predicted by using recently published data bases on RHA penetration to determine the residual penetration into the steel back-up of the DOP test. Results of this methodology, compared to experimental DOP-test results, agree reasonably well for aluminum nitride and silicon carbide, even though scale sizes, impact velocities and experimental procedures varied considerably between investigators. The methodology was then applied to single-valued performance criteria for ceramic armor materials, for example, mass efficiency. This analysis demonstrates that in certain cases, test parameters, like the ratio of penetrator length to ceramic tile thickness, affect test results considerably more than differences between ceramic types. Thus, DOP tests must be properly designed and interpreted in order to assess correctly the ballistic performance of ceramics.
[85] Franzen R R, Walker J D, Orphal D L, Anderson Jr C E.1994.

An upper limit for the penetration performance of segmented rods with segment-$L/D \leq 1$

. International Journal of Impact Engineering, 15: 661-668.

DOI      URL      摘要

ABSTRACT This study investigates the question of whether the penetration performance of a segmented rod penetrator with segment-L/D 81 1 can exceed that of a uniform density continuous rod of equal mass, length (including spaces), diameter and velocity (“comparison rod”). The answer, based on experimental, computational and analytical data published to-date, is negative. The well-known fact that segmented rods penetrate better than their so-called “parent rods” (rods of equal mass, diameter and velocity and a length equal to the sum of segment lengths only), together with findings presented here, limits the penetration performance of segmented rods to Pparent rod < Psegmented rod < Pcomparison rod· The limitations of the data base used here may limit the generality of the findings: in particular, the database is fairly small, only unyawed, normal impacts at velocities of 2 km/s and higher are included, and, with few exceptions, only tungsten segments and steel targets were studied.
[86] Galanov B A, Kartuzov V V, Ivanov S M.2008.

New analytical model of expansion of spherical cavity in brittle material based on the concepts of mechanics of compressible porous and powder materials

. International Journal of Impact Engineering, 35: 1522-1528.

DOI      URL      [本文引用: 1]      摘要

In this paper, the concepts of mechanics of porous and powder media are applied for development of new analytical model of expansion of spherical cavity in brittle materials. The model is based on the approach that recognizes the existence of three regions with different rheology: region of comminuted and compacted material; region of pore formation formed by radial cracks; elastically deformed region. Strain-stress state in each region is determined and analyzed. Cavity expansion pressure is determined. Energy losses on elastic deformation, fracture and compaction of material are calculated and compared for a number of ceramic materials. It is shown that the contribution of compaction and fracture in total energy losses is considerable. The presented model avoids the use of rheological characteristics that are difficult to determine and uses instead the porosity of the material.[All rights reserved Elsevier].
[87] Gold V M, Vradis G C, Pearson J C.1996.

Concrete penetration by eroding projectiles: Experiments and analysis

. Journal of Engineering Mechanics, 122: 145-152.

DOI      URL      [本文引用: 1]     

[88] Goldsmith W.1999.

Non-ideal projectile impact on targets

. International Journal of Impact Engineering, 22: 95-395.

DOI      URL      [本文引用: 4]      摘要

Sufficient technical information is presented to provide a reasonable assessment of the character, approach and results obtained for the various studies. If more detailed information concerning analytical or experimental procedures are required, the reader should consult the original references which are fully listed.
[89] Grabarek C L.1971.

Penetration of Armor by Steel and High Density Penetrators (U)

. Ballistic Research Laboratories.

URL      [本文引用: 2]     

[90] Hauver G, Gooch W, Netherwood P, Benck R, Perciballi W, Burkins M.1992.

Variation of target resistance during long-rod penetration into ceramics//Proceedings of the 13th International Symposium on Ballistics,

Sundyberg, Sweden: 257-264.

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[91] He Y, Wen H M.2013.

Predicting the penetration of long rods into semi-infinite metallic targets

. Science China (Technological Sciences), 56: 2814-2820.

DOI      URL      [本文引用: 4]      摘要

Analytical equations are presented herein to predict the penetration of semi-infinite metallic targets struck normally by long rods at high velocities for Y p < S where Y p is the rod strength and S is the static target resistance. The equations are derived based on energy balance method. It is assumed that the kinetic energy loss of a long rod is related to the energy dissipated by the plastic deformations in the target, the energy consumed by the long-rod penetrator itself and the energy carried by the eroded rod debris. Secondary penetration is also examined in the present paper due to the fact that the eroded rod debris forms a tube which can penetrate the target further if the density of the rod is greater than that of the target and the impact velocity is high enough. The present analytical equation is found to be in good agreement with the experimental data for a wide range of impact velocities.
[92] Herrmann W, Wilbeck J S.1987.

Review of hypervelocity penetration theories

. International Journal of Impact Engineering, 5: 307-322.

DOI      URL      [本文引用: 4]      摘要

A review is given of the emperical and approximate theoretical expressions which have been developed to describe various aspects of impact at hypervelocities where the projectile and some of the target materials undergo massive plastic deformation, breakup, melting or vaporization. Various stages of the penetration process are identified on the basis of experimental evidence. Empirical fits to experimental data, or, at velocities above the experimental range, to results of finite difference calculations of the penetration event, are reviewed. In some cases simple theories, usually requiring the evaluation of some undetermined parameters from experimental or numerical data, have been developed. These are described, with emphasis on those which have found use in the design of offensive or defensive systems.
[93] Hetherington J G, Lemieux P F.1994.

The effect of obliquity on the ballistic performance of two component composite armours

. International Journal of Impact Engineering, 15: 131-137.

DOI      URL      [本文引用: 1]      摘要

ABSTRACT This paper examines the performance of composite armours when subjected to oblique impact. Experimental results are presented from a programme of trials on ceramic-aluminium targets using 7.62 mm ball ammunition. The results show that an inclined ceramic composite armour plate will perform better, on a thickness basis, than one arranged perpendicular to the line of impact. However, the degree of improvement thus obtained is much less than for steel armours. Moreover, it is shown that minimum weight protection to a vulnerable area, using ceramic composite armours, is achieved when the armour is perpendicular to the threat. The degree of thickness reduction which is obtained by angling ceramic composite armours is much less than for steel armours. A theoretical model of oblique impact is presented and shown to correlate well with the experimental results.
[94] Hirt C W, Amsden A A, Cook J L.1974.

An arbitrary Lagrangian-Eulerian computing method for all flow speeds

. Journal of computational physics, 14: 227-253.

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[95] Hohler V, Behner T.1999.

Influence of the yaw angle on the performance reduction of long rod projectiles//Proceedings of the 18th international symposium on ballistics,

Antonio, TX: 931-938.

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[96] Hohler V, Rothenhausler H, Schneider E, Senf H, Stilp A J, Tham R.

Untersuchung der Shockwirkung auf Panzerfahrzeuge

. Ernst Mach Institute Report, 1978.

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[97] Hohler V, Stilp A J.1977.

Penetration of steel and high density rods in semi-infinite steel targets//Proceedings of the 3rd international symposium on ballistics

.

[98] Hohler V, Stilp A J.1987.

Hypervelocity impact of rod projectiles with L/D from 1 to 32

. International Journal of Impact Engineering, 5: 323-331.

DOI      URL      [本文引用: 9]      摘要

Beside a short remark on the “hydrodynamic theory of rod projectiles”, the paper deals with the terminal ballistic behaviour of cylindrical projectiles against semi-infinite targets. Experimental data of EMI, completed by results of some other authors, are presented. Crater parameters like depth, diameter and volume and their dependence on projectile velocity (up to 5000 m/s), projectile and target material properties, as well as L/D-ratios (1–32), will be discussed. Mainly the projectile materials steel and tungsten sinter-alloys are considered. Target materials are mild steel and high strength steel, an Al-alloy and a tungsten sinter-alloy. The results show that the influence of material density on the crater dimensions is considerably greater than the influence of strength. The L/D ratio determines the velocity dependence of crater depth, diameter and volume. At high velocities in the hydrodynamic regime, the crater depth of short cylinders (L/D 65 1) is approximately proportional to v p 2/3 (V p=projectile velocity). With increasing L/D-ratio, the slope of the penetration curves decreases and converges for rods (L/D 62 1) versus a saturation, i. e. becomes nearly independent on v p. A consequence of this saturation is the existence of a so-called “tangent velocity”, above which an optimal increase of efficiency is only realized by increasing the projectile mass and not the velocity. Furthermore, ballistic limits of real targets like single plates and symmetric double plates meteorite bumper shield) are taken into account. The expected better performance of “segmented rods” is also discussed.
[99] Hohler V, Stilp A J, Walker J D, Anderson C E.1993.

Penetration of long rods into steel and glass targets: Experiments and computations

. Annals of Clinical Psychiatry, 29: 211-217.

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[100] Hohler V, Stilp A J, Weber K.1995.

Hypervelocity penetration of tungsten sinter-alloy rods into aluminum

. International Journal of Impact Engineering, 17: 409-418.

DOI      URL      [本文引用: 7]      摘要

The penetration of tungsten sinter-alloy rods having length-to-diameter ratios of L/D= 10 and 12.5 into alumina targets was investigated in the velocity range v p = 1.25 to 3km/s. The depth of penetration (DOP) test and the time resolved oberservation using a 600 kV flash X-ray system were applied to assess the protection efficiency of the ceramics. From DOP tests, the residual penetration into a steel backing yields the differential efficiency factor DEF and the mass efficiency factor MEF. DEF increases with v p ; MEF decreases. On the other hand, DEF decreases as ceramic thickness increases; MEF increases and converges to DEF for residual penetration zero. From the time resolved measurements, position and length reduction of the rod during penetration in the ceramics were obtained. The process can be described by Tate's fluid jet model in good approximation. The target resistance parameter R, defined in the modified Bernoulli equation, characterizes the ceramic performance. The average R values are 5.4, 6.1 and 4.8 GPa at impact velocities v p = 1.7, 2.5 and 3km/s, respectively, i.e. there is no strong dependence of R on v p .
[101] Hohler V, Stilp A.2002.

Penetration performance of segmented rods at different spacing-comparison with homogeneous rods at 2.5-3.5km/s

. Journal of Neuroscience the Official Journal of the Society for Neuroscience, 22: 2541-2549.

DOI      URL      [本文引用: 1]     

[102] Hohler V, Weber K, Tham R, James B, Barker A, Pickup I.2001.

Comparative analysis of oblique impact on ceramic composite systems

. International Journal of Impact Engineering, 26: 333-344.

DOI      URL      [本文引用: 1]      摘要

An experimental programme is presented which investigated the performance of oblique, ceramic/metal, bilayer composite armours. The ceramics, alumina and silicon carbide, were backed by either Rolled Homogeneous Armour steel (RHA) or 7000 series aluminium. Using a model scale tungsten penetrator at two velocities (representing current and future ordnance threats) the effect of configuration on ballistic limit or depth of penetration (DOP) areal densities was determined. Areal densities of the DOP targets decreased with increasing ceramic thickness, achieving a minimum at zero residual penetration in the backing. The bilayer targets, loaded at the ballistic limit needed a larger areal density to defeat the penetrator. This areal density also decreased with ceramic thickness but showed a minimum with respect to ceramic thickness, as a result of reduced support by the thinner metallic backing. At 1450ms 1 the most efficient system was found to be a SiC/Al, which demonstrated a 25% weight saving over the monolithic aluminium reference target. The Al-alloy backing performs better than RHA, and SiC better than Al 2O 3.
[103] Holmquist T J, Anderson C E, Behner T, Orphal D L.2010.

Mechanics of dwell and post-dwell penetration

. Advances in Applied Ceramics, 109: 467-479.

DOI      URL      [本文引用: 6]      摘要

Abstract
[104] Holmquist T J, Johnson G R.2003.

Modeling projectile impact onto prestressed ceramic targets

. Journal De Physique IV, 110: 597-602.

DOI      URL      [本文引用: 2]      摘要

This work presents computed results for the responses of ceramic targets, with and without prestress, subjected to projectile impact. Also presented is a computational technique to include prestress. Ceramic materials have been considered for armor applications for many years because of their high strength and low density. Many researchers have demonstrated that providing confinement enhances the ballistic performance of ceramic targets. More recently, prestressing the ceramic is being considered as an additional enhancement technique. This work investigates the effect of prestressing the ceramic for both thin and thick target configurations subjected to projectile impact. In all cases the targets with ceramic prestress provided enhanced ballistic performance. The computed results indicate that prestressed ceramic reduces and/or delays failure, resulting in improved ceramic performance and ballistic efficiency.
[105] Holmquist T J, Johnson G R.2005.

Modeling prestressed ceramic and its effect on ballistic performance

. International Journal of Impact Engineering, 31: 113-127.

DOI      URL      [本文引用: 2]      摘要

This article presents computed results for the responses of ceramic targets, with and without prestress, subjected to projectile impact. Also presented is a computational technique to include prestress. Thin and thick ceramic target configurations are used to understand the effect prestressing has on ballistic performance. For both targets two prestress levels (small and large), and two prestress states (radial and hydrostatic) are investigated. The small prestress is similar in magnitude to values obtained experimentally and the large prestress is approximately the maximum prestress the confinement can produce (determined computationally). The targets are subjected to projectile impact and the resulting ballistic responses are evaluated. In all cases prestressing the ceramic enhanced the ballistic performance, although the effect of the different prestress conditions on the ballistic response was not always obvious.
[106] Holmquist T J, Johnson G R.2011.

A Computational Constitutive Model for Glass Subjected to Large Strains, High Strain Rates and High Pressures

. Journal of Applied Mechanics, 78: 51003.

DOI      URL      [本文引用: 1]      摘要

This article presents a computational constitutive model for glass subjected to large strains, high strain rates and high pressures. The model has similarities to a previously developed model for brittle materials by Johnson, Holmquist and Beissel (JHB model), but there are significant differences. This new glass model provides a material strength that is dependent on the location and/or condition of the material. Provisions are made for the strength to be dependent on whether it is in the interior, on the surface (different surface finishes can be accommodated), adjacent to failed material, or if it is failed. The intact and failed strengths are also dependent on the pressure and the strain rate. Thermal softening, damage softening, time-dependent softening, and the effect of the third invariant are also included. The shear modulus can be constant or variable. The pressure-volume relationship includes permanent densification and bulking. Damage is accumulated based on plastic strain, pressure and strain rate. Simple (single-element) examples are presented to illustrate the capabilities of the model. Computed results for more complex ballistic impact configurations are also presented and compared to experimental data. [DOI: 10.1115/1.4004326]
[107] Holmquist T J, Johnson G R, Cook W H.1993.

A computational constitutive model for concrete subjected to large strains, high strain rates and high pressures//Proceedings of 14th international symposium on Ballistics, Quebec, Canada

.

[本文引用: 1]     

[108] Islam M J, Swaddiwudhipong S, Liu Z S.2013.

Penetration of concrete targets using a modified Holmquist-Johnson-Cook material model

. International Journal of Computational Methods, 9: 185-197.

DOI      URL      [本文引用: 1]      摘要

For concrete target penetration and/or perforation simulation, the Holmquistu2013Johnsonu2013Cook (HJC) material model is widely used as concrete material model. However, the strain rate expression of the model has failed to explain the sudden increase in concrete strength at high strain rates. The pressure-volume relationship of the HJC model is complex and requires a large number of material constants. In this study, a modified Holmquistu2013Johnsonu2013Cook (HJC) model is proposed for concrete material under high velocity impact. The modification involves simplification and improvement of the strain rate expression and pressure-volume relationship. Material parameters identification procedure for the MHJC model is also elaborated. The numerical simulations using the proposed model show a good agreement with experimental observations, especially, on the residual velocities, penetration depths and failure patterns of the target plates. These validate the applicability of the MHJC model for high velocity projectile impac...
[109] Jiao W J, Chen X W.2018.

Approximate solutions of the Alekseevskii--Tate model of long-rod penetration

. Acta Mechanica Sinica, 34: 334-348.

DOI      URL      [本文引用: 4]      摘要

The Alekseevskii–Tate model is the most successful semi-hydrodynamic model applied to long-rod penetration into semi-infinite targets. However, due to the nonlinear nature of the equations, the rod(tail) velocity, penetration velocity, rod length, and penetration depth were obtained implicitly as a function of time and solved numerically By employing a linear approximation to the logarithmic relative rod length, we obtain two sets of explicit approximate algebraic solutions based on the implicit theoretica solution deduced from primitive equations. It is very convenient in the theoretical prediction of the Alekseevskii–Tate model to apply these simple algebraic solutions. In particular, approximate solution 1 shows good agreement with the theoretical(exact) solution, and the first-order perturbation solution obtained by Walters et al.(Int. J. Impac Eng. 33:837–846, 2006) can be deemed as a special form of approximate solution 1 in high-speed penetration. Meanwhile, with constant tail velocity and penetration velocity approximate solution 2 has very simple expressions, which is applicable for the qualitative analysis of long-rod penetration. Differences among these two approximate solutions and the theoretical(exact) solution and their respective scopes of application have been discussed, and the inferences with clear physical basis have been drawn. In addition, these two solutions and the first-order perturbation solution are applied to two cases with different initial impact velocity and different penetrator/target combinations to compare with the theoretical(exact) solution. Approximate solution 1 is much closer to the theoretical solution of the Alekseevskii–Tate model than the first-order perturbation solution in both cases, whilst approximate solution 2 brings us a more intuitive understanding of quasi-steady-state penetration.
[110] Johnson G R, Cook W H.1983.

A constitutive model and data for metals subjected to large strains, high strain rates and high temperatures//Proceedings of the 7th International Symposium on Ballistics:

541-547.

[本文引用: 2]     

[111] Johnson G R, Holmquist T J.1994.

An improved computational constitutive model for brittle materials

. High Pressure Science and Technology, 309: 981-984.

DOI      URL      [本文引用: 3]      摘要

An improved computational constitutive model for brittle materials is presented. It is applicable for brittle materials subjected to large strains, high strain rates and high pressures, and is well锕晆ited for computations in both Lagrangian and Eulerian codes. The equivalent strength is dependent on the intact strength, fractured strength, strain rate, pressure, and damage. The pressure includes the effect of bulking, which is introduced through the transfer of internal energy from decreased shear and deviator stresses to potential internal energy associated with increased hydrostatic pressure. Examples are presented to illustrate the model.
[112] Johnson G R, Holmquist T J, Beissel S R.2003.

Response of aluminum nitride (including a phase change) to large strains, high strain rates, and high pressures

. Journal of Applied Physics, 94: 1639-1646.

DOI      URL      [本文引用: 1]      摘要

This article contains a description of a computational constitutive model for brittle materials subjected to large strains, high strain rates, and high pressures. The focus of this model is to determine the response of aluminum nitride under high velocity impact conditions that produce large strains, high strain rates, and high pressures. The strength is expressed as a function of the pressure, strain rate, and accumulated damage; and it allows for strength of both intact and failed material. The pressure is primarily expressed as a function of the volumetric strain, but it also includes the effect of bulking for the failed material. For materials without a phase change this model is an extension of the previous Johnson olmquist models for brittle materials. The primary new feature of this model is the capability to include a phase change, and this is required for aluminum nitride. Computations are performed to illustrate the capabilities of the model, to compare computed results to experimental results,...
[113] Johnson G R, Stryk R A.2003.

Conversion of 3D distorted elements into meshless particles during dynamic deformation

. International Journal of Impact Engineering, 28: 947-966.

DOI      URL      [本文引用: 1]      摘要

This paper presents a description of an algorithm to automatically convert 3D distorted elements into meshless particles during dynamic deformation. It also includes an improved (invariant) particle algorithm that allows for a more accurate treatment of boundaries and interfaces. These new 3D algorithms have been incorporated into an explicit Lagrangian code that includes both elements and particles. They provide for increased capability and accuracy for Lagrangian computations involving severe distortions. Several 3D examples are included to demonstrate the new technique.
[114] Johnson G R, Stryk R A, Beissel S R, Holmquist T J.2002.

An algorithm to automatically convert distorted finite elements into meshless particles during dynamic deformation

. International Journal of Impact Engineering, 27: 997-1013.

DOI      URL      [本文引用: 2]      摘要

This paper presents an explicit 2D Lagrangian algorithm to automatically convert distorted elements into meshless particles during dynamic deformation. It also provides the contact and sliding algorithms to link the particles to the finite elements. For this approach the initial grid is composed entirely of finite elements and the response is computed with finite elements until portions of the grid become highly strained. When finite elements on the boundaries reach a user-specified plastic strain they are converted to particles and linked to the adjacent finite element grid. This approach allows for the use of accurate and efficient finite elements in the lower distortion regions, and for the use of meshless particles in the higher distortion regions. Example computations are presented to demonstrate the accuracy and utility of this approach.
[115] Kong X Z, Fang Q, Li Q M, Wu H, Crawford J E.2017a.

Modified K & C model for cratering and scabbing of concrete slabs under projectile impact

. International Journal of Impact Engineering, 108: 217-228.

DOI      URL      [本文引用: 1]     

[116] Kong X Z, Fang Q, Wu H, Peng Y.2016a.

Numerical predictions of cratering and scabbing in concrete slabs subjected to projectile impact using a modified version of HJC material model

. International Journal of Impact Engineering, 95: 61-71.

DOI      URL      [本文引用: 1]      摘要

The HJC material model, which has been widely used for numerical predictions of projectile penetration, is modified for the improved numerical simulations of the cratering and scabbing phenomenon in concrete slabs subjected to projectile impact. Four modifications, i.e. the modified yield surface, introduction of the tensile damage, introduction of Lode-angle dependency and modified strain-rate effect, are presented. The modified HJC model is implemented into the finite element code LS-DYNA through user defined material model. The improved performances due to the modifications are firstly demonstrated by single finite element numerical tests. And then several sets of projectile perforation experiments, in which the projectile mass, impact velocity and concrete slab thickness vary, are simulated by the modified HJC model, where corresponding predictions of the original HJC model are also presented to demonstrate the improved simulation of the cratering and scabbing phenomenon. Sensitivity analysis of three independent parameters that govern the tensile dynamic behavior of the modified model shows that the fracture strain and dynamic increase factor for tension are crucial for the correct modeling of the scabbing phenomenon, and the dynamic increase factor for tension as well as the ratio of the current meridian to the compressive meridian are important for the simulation of the cratering phenomenon.
[117] Kong X, Li Q M, Fang Q.2016b.

Critical Impact Yaw for Long-Rod Penetrators

. Journal of Applied Mechanics, 83: 121008.

DOI      URL      [本文引用: 2]      摘要

Abstract This paper presents an improved model for the critical impact yaw (or simply the critical yaw) in long-rod penetration with considering the deceleration and rotation of the rod and the crater shape of the target. Two critical yaws, θc1 and θc2, under normal impact were identified, below which there is no contact between the rod and crater sidewall (for θc1) and between the rod and the crater entrance (for θc2) during the entire penetration process. Contact functions and iterative algorithms were proposed in order to obtain these two critical yaws numerically. The influences of four dominant nondimensional numbers (i.e., the ratio of the target resistance to the rod strength λ, Johnson's damage number of the rod ζ, square root of the target-projectile density ratio μ, and the diameter-length ratio of the rod ψ) on two critical yaws were studied for three typical rod-target systems (tungsten alloy rods penetrating steel targets, steel rods penetrating aluminum alloy targets, and steel rods penetrating steel targets). The relationship between two critical yaw angles was also discussed. A new empirical formula for the critical yaw θc2 was proposed based on the parametric study results and dominant nondimensional numbers, which extends the valid application range of the existing empirical formula.
[118] Kong X Z, Wu H, Fang Q, Peng Y.2017b.

Rigid and eroding projectile penetration into concrete targets based on an extended dynamic cavity expansion model

. International Journal of Impact Engineering, 100: 13-22.

DOI      URL      [本文引用: 3]      摘要

A hyperbolic yield criterion and Murnaghan equation of state were introduced to describe the plastic behavior of concrete material under projectile penetration, and an extended dynamic cavity expansion model was proposed. Then, a unified one-dimensional resistance of concrete target to projectile penetration was formulated, in which the projectile nose shape influences were taken into account by three non-dimensional coefficients. Furthermore, combined with the Newton's second law and Alekseevskii-Tate equations, both rigid and eroding projectile penetration models into concrete targets were established. By comparing with the existing tests data as well as prediction results of previous model based on the linear yield criterion and equation of state, the proposed models were verified. Besides, a series of practical parameters of hyperbolic yield criterion and Murnaghan EOS for the extended dynamic cavity expansion model were given and verified.
[119] Kong X Z, Wu H, Fang Q, Zhang W, Xiao Y K.2017

c. Projectile penetration into mortar targets with a broad range of striking velocities: Test and analyses

. International Journal of Impact Engineering, 106: 18-29.

DOI      URL      [本文引用: 5]      摘要

Eighteen shots of flat nosed cylindrical 45# steel projectiles penetrating into mortar targets with cubic compressive strength of 50 MPa are conducted, where the striking velocities are ranged from 510 m/s to 1850 m/s. By examining the damages of targets, linear dependences of the cratering diameter and depth on the initial striking velocity, as well as the cratering volume on the initial kinetic energy of projectile are found. Three penetration regimes, i.e., rigid projectile penetration, deforming projectile penetration without eroding and eroding projectile penetration are observed successively with the increase of striking velocity. Furthermore, the experimental depths of penetration are compared with the predictions of our recently established rigid and eroding penetration models based on an extended dynamic cavity expansion model (Kong et al. 2017). The rigid projectile penetration model is further validated, and the eroding projectile penetration model is further justified, improved and validated by considering the succeeding rigid penetration stage. Finally, the analytical expressions for the upper limit velocity of rigid projectile penetration and the lower limit velocity of eroding projectile penetration are given and validated, respectively.
[120] Lambert J P.1978.

A residual velocity predictive model for long rod penetrators

. Aberdeen Proving Ground, BRL, Report No. ARBRL-MR-02828.

[本文引用: 2]     

[121] Lan B, Wen H M.2010.

Alekseevskii-Tate revisited: An extension to the modified hydrodynamic theory of long rod penetration

. Science China Technological Sciences, 53: 1364-1373.

DOI      URL      [本文引用: 5]      摘要

The modified hydrodynamic theory of long rod penetration into semi-infinite targets was established independently by Alek-seevskii and Tate over forty years ago and since then many investigators contributed much to the development of the high speed penetration mechanics.However,in all the models proposed so far,the target resistance Rt is not well defined and usually determined by adjusting it until the predicted depth of penetration comes to an agreement with experimental data.In this paper,assumptions are first made about particle velocity and pressure profiles together with response regions in the target and then an extension is made to the modified hydrodynamic theory of long rod penetration into semi-infinite targets,in which Rt has explicit form and is dependent on penetration velocity as well as thermo-mechanical properties of target material.The present model is compared with long rod penetration tests for different material combinations.It transpires that the present model predictions are in good agreement with the experimental data and numerical simulations in terms of penetration depth although many assumptions and simplifications are introduced into the paper.
[122] Lee M.2000.

An engineering impact model for yawed projectiles

. International Journal of Impact Engineering, 24: 797-807.

DOI      URL      [本文引用: 2]      摘要

When a long-rod projectile penetrates a thick target with an angle of attack, interfering of the projectile with the sidewall of a crater is the mechanism for the degraded penetration performance. By using an engineering model, significant parameters and how they vary over a wide velocity range can be quickly obtained. A transient discreet impact model is developed to predict not only the crater profile but final depth generated by the penetration of a yawed long rod. The yawed long rod is described as a series of continuous finite disk elements which enables us to keep revising the time-dependent crater profile. To consider the interaction with the crater sidewall, effective diameters for each element are used, and the revised crater profile is calculated based on these effective diameters. Three possibilities of the degree of degradation in penetration for the elements that interact with crater sidewall are discussed. The model reduces, in the case of the impact with no yaw, to the Alekseevskii ate's solution. Theoretical predictions are compared with the corresponding experimental data.
[123] Lee M.2003.

Hypervelocity impact into oblique ceramic/metal composite systems

. International Journal of Impact Engineering, 29: 417-424.

DOI      URL      [本文引用: 2]      摘要

A numerical study for the analysis of oblique ceramic/metal composite armour systems against L/D = 20 projectiles has been performed. The ballistic performance of the add-on lightweight armours was examined by determiningthe effect of areal density of the system on ballistic limit or depth of penetration (DOP). To do this, a series of three-dimensional numerical simulations has been conduced. The impact velocities considered are 2.2 and 2.6 km/s. The oblique angle of the plate is 60 degrees. Simulation results for ballistic limits appear to match fairly well with the test values. Although the previous data for the penetration of 7.62 AP projectile into relatively thin alumina/aluminium composite targets revealed an optimum value of the front plate to back plate thickness ratio in the region of 1.5, the current data for the impact of long rod into relatively thick composite targets are scattering. This is because the distinguishing features of thin composite armour systems against 7.62 AP and 40.7g steel projectiles are crack propagation, ceramic conoid formation and failure of backing plate, while these effects are less significant in thick targets, especially at high impact velocities.
[124] Lee M, Bless S J.1998.

Cavity models for solid and hollow projectiles

. International Journal of Impact Engineering, 21: 881-894.

DOI      URL      [本文引用: 1]      摘要

ABSTRACT Two analytical models for the crater size generated by long-rod and thick-walled tube projectiles are presented. The first is based on energy; in a steady-state penetration, the kinetic energy loss of a projectile is related to the total energy deposited in the target. This simple approach provides an upper bound for the crater size. The second approach is based on the observation that two mechanisms are involved in cavity growth due to long projectiles: flow of projectile erosion products, which exerts radial stress on the target and opens a cavity, and radial momentum of the target as it flows around the projectile nose (cavitation). This analysis includes the centrifugal force exerted by the projectile, radial momentum of the target, and the strength of the target. Thus, it can estimate the extent of cavity growth due to projectile mushrooming, which cannot be predicted by other analyses. This model is shown to be in good agreement with experimental data.
[125] Lee M, Bless S.1996.

Cavity dynamics for long rod penetration

. The Univercity of Texas at Austin Institute for Advanced Technology.

[本文引用: 1]     

[126] Lee W, Lee H, Shin H.2002.

Ricochet of a tungsten heavy alloy long-rod projectile from deformable steel plates

. Journal of Physics D: Applied Physics, 35: 2676.

DOI      URL      [本文引用: 2]      摘要

Ricochet of a tungsten heavy alloy long-rod projectile from oblique steel plates with a finite thickness was investigated numerically using a full three-dimensional explicit finite element method. Three distinctive regimes resulting from oblique impact depending on the obliquity, namely simple ricochet, critical ricochet and target perforation, were investigated in detail. Critical ricochet angles were calculated for various impact velocities and strengths of the target plates. It was predicted that critical ricochet angle increases with decreasing impact velocities and that higher ricochet angles were expected if higher strength target materials are employed. Numerical predictions were compared with existing two-dimensional analytical models. Experiments were also carried out and the results supported the predictions of the numerical analysis.
[127] Li J C, Chen X W.2017.

Theoretical analysis of projectile-target interface defeat and transition to penetration by long rods due to oblique impacts of ceramic targets

. International Journal of Impact Engineering, 106: 53-63.

DOI      URL      [本文引用: 5]     

[128] Li J C, Chen X W, Huang F L.2015a.

FEM analysis on the “self-sharpening” behavior of tungsten fiber/metallic glass matrix composite long rod

. International Journal of Impact Engineering, 86: 67-83.

DOI      URL      [本文引用: 6]      摘要

612-D and 3-D models of composite rod are established based on its innerstructure.61A modified constitutive model is employed to describe the metallic glass matrix.61The mechanism of “self-sharpening” for the composite rod is analyzed in detail.61The effects of various factors on the “self-sharpening” behavior are discussed.
[129] Li J C, Chen X W, Ning F.2014.

Comparative analysis on the interface defeat between the cylindrical and conical-nosed long rods

. International Journal of Protective Structures, 5: 21-46.

DOI      URL      [本文引用: 3]     

[130] Li J C, Chen X W, Ning F, Li X L.2015b.

On the transition from interface defeat to penetration in the impact of long rod onto ceramic targets

. International Journal of Impact Engineering, 83: 37-46.

DOI      URL      [本文引用: 6]      摘要

61Three deformation modes of the long rod and the ceramic target are summarized.61The critical impact velocity range for the transition is further identified.61Critical transition time is analyzed and an analytical expression is formulated.61The analytical formula is convenient for the engineering application.
[131] Li J Z, Zhang L S, Huang F L.2017.

Experiments and simulations of tungsten alloy rods penetrating into alumina ceramic/603 armor steel composite targets

. International Journal of Impact Engineering, 101: 1-8.

DOI      URL      [本文引用: 4]      摘要

The experiments and numerical simulations of tungsten alloy rods penetrating into alumina ceramic/603 armor steel composite target were conducted. Both the experiments and numerical simulations produced measurements of residual penetration depths in the steel back plates. The numerical simulations also showed damage distribution during the penetrating process. This study concludes that the residual penetration depth decreases linearly with increasing ceramic thickness. Therefore, both the mass efficiency factor and the differential efficiency factor increase with increasing ceramic thickness. The ceramic was seriously comminuted at the impact site and split into very small fragments whose sizes depend on the distance from the impact site. The ceramic targets without lateral constraint were more severely pulverized due to the tensile stress reflected from the lateral boundary.
[132] Li Q M, Chen X W.2003.

Dimensionless formulae for penetration depth of concrete target impacted by a non-deformable projectile

. International Journal of Impact Engineering, 28: 93-116.

DOI      URL      摘要

Based on the dimensional analysis of concrete penetration by a non-deformable projectile and an analytical penetration model, two dimensionless numbers, i.e., the impact function I and the geometry function of projectile N are defined and used in a dimensionless formula to predict the penetration depth. It is shown that experimental data on shallow, medium and deep penetrations in a broad range of concrete strength, impact velocity and projectile geometry can be uniquely represented by these two dimensionless numbers. It is also shown that the formula based on these two dimensionless numbers is comparable to the unit-dependent empirical formulae on penetration depth.
[133] Littlefield D L, Anderson Jr C E, Partom Y, Bless S J.1997.

The penetration of steel targets finite in radial extent

. International Journal of Impact Engineering, 19: 49-62.

DOI      URL      [本文引用: 1]      摘要

An experimental, analytical, and computational effort was undertaken to examine the effect of confinement on penetration in armor-like steel targets. For the experiments, LD 10, tungsten-alloy projectiles were fired at 1.5 km/s into 4340 steel cylindrical rounds of various diameters. Penetration efficiencies, as measured by the depth of penetration normalized by the original projectile length (PL), were determined and the results plotted as a function of normalized target diameter DD, where Dis the target diameter and D is the projectile diameter. As DD changed from 20 to 5, PL increased by 28%, although PL was approximately independent of DD for DD ? 15. An analytical model using a modified cavity expansion theory was developed to estimate the resistance to penetration for targets of finite lateral extent. The analytical model shows decreasing target resistance as DD decreases below approximately 30; in particular, target resistance decreases rapidly forDD < 20. Numerical simulations were performed and the computational predictions are in excellent agreement with the experimental results; simulations were used to extend DD between 3 and 78. Plastic strain contours are plotted to assess the extent of plastic flow within the target; the results of the simulations demonstrate thatPL begins to increase when the extent of plastic flow in the target reaches the radial boundary.
[134] Liu J C, Pi A G, Huang F L.2015.

Penetration performance of double-ogive-nose projectiles

. International Journal of Impact Engineering, 84: 13-23.

DOI      URL      [本文引用: 1]      摘要

61A double-ogive-nose penetration body scheme with a low penetration resistance is proposed.61The influence of the nose shape coefficient N65 on the penetration resistance and DOP is discussed.61The feasibility of the proposed method is validated through theoretical, experimental, and simulation results.
[135] Liu Y, Ma A, Huang F L.2009.

Numerical simulations of oblique-angle penetration by deformable projectiles into concrete targets

. International Journal of Impact Engineering, 36: 438-446.

DOI      URL      [本文引用: 1]      摘要

Numerical simulations of oblique-angle penetration by deformable projectiles into concrete targets are performed in this paper by using the three-dimensional finite element code LS-DYNA, into which a combined dynamic constitutive model which can simultaneously describe both the compressive and tensile damage of concrete is implemented. As a consequence, the ballistic trajectories and the depths of penetration under different oblique angles (from 10 to the ricochet angle) are obtained. Moreover, the damage distribution of concrete after oblique penetration is procured, which can really reflect the tensile and compressive damage of concrete. The numerical results for the depths of penetration are compared with experimental data obtained by previous authors and show good agreement.
[136] Lu Z C, Wen H M.2018.

On the penetration of high strength steel rods into semi-infinite aluminium alloy targets

. International Journal of Impact Engineering, 111: 1-10.

DOI      URL      [本文引用: 3]     

[137] Lundberg P, Renström R, Andersson O.2013.

Influence of length scale on the transition from interface defeat to penetration in unconfined ceramic targets

. Journal of Applied Mechanics, 80: 979-985.

DOI      URL      [本文引用: 4]      摘要

One observation from interface defeat experiments with thick ceramic targets is that confinement and prestress becomes less important if the test scale is reduced. A small unconfined target can show similar transition velocity as a large and heavily confined target. A possible explanation for this behavior is that the transition velocity depends on the formation and growth of macro cracks. Since the crack resistance increases with decreasing length scale, the extension of a crack in a small-scale target will need a stronger stress field, viz., a higher impact velocity, in order to propagate. An analytical model for the relation between projectile load, corresponding stress field, and the propagation of a cone-shaped crack under a state of interface defeat has been formulated. It is based on the assumption that the transition from interface defeat to penetration is controlled by the growth of the cone crack to a critical length. The model is compared to experimentally determined transition velocities for ceramic targets in different sizes, representing a linear scale factor of ten. The model shows that the projectile pressure at transition is proportional to one over the square root of the length scale. The experiments with small targets follow this relation as long as the projectile pressure at transition exceeds the bound of tensile failure of the ceramic. For larger targets, the transition will become independent of length scale and only depend on the tensile strength of the ceramic material. Both the experiments and the model indicate that scaling of interface defeat needs to be done with caution and that experimental data from one length scale needs to be examined carefully before extrapolating to another.
[138] Lundberg P, Lundberg B.2005.

Transition between interface defeat and penetration for tungsten projectiles and four silicon carbide materials

. International Journal of Impact Engineering, 31: 781-792.

DOI      URL      [本文引用: 7]     

[139] Lundberg P, Renström R, Lundberg B.2000.

Impact of metallic projectiles on ceramic targets: Transition between interface defeat and penetration

. International Journal of Impact Engineering, 24: 259-275.

DOI      URL      [本文引用: 8]      摘要

Armour systems capable of defeating an incoming projectile on the surface of a ceramic have been reported by several authors. This capability, called interface defeat, signifies that the projectile material is forced to flow radially outwards on the surface of the ceramic without penetrating significantly. In order to investigate the conditions for interface defeat, two models for the interaction of a metallic projectile and a ceramic target were established. With the aid of them, upper and lower bounds for the transition impact velocity between interface defeat and normal penetration were estimated for a given combination of metallic projectile and ceramic target. These approximate bounds were found to be consistent with transition velocities determined experimentally for two projectile materials (tungsten and molybdenum) and five target materials (two types of silicon carbide, boron carbide, titanium diboride and a polycrystalline diamond composite).
[140] Lundberg P, Renström R, Lundberg B.2006.

Impact of conical tungsten projectiles on flat silicon carbide targets: Transition from interface defeat to penetration

. International Journal of Impact Engineering, 32: 1842-1856.

DOI      URL      [本文引用: 4]      摘要

Normal impact of conical tungsten projectiles on flat silicon carbide targets was studied experimentally and numerically for half apex angles 5 and 5 15 , respectively, and comparisons were made with cylindrical projectiles. A 30 mm powder gun and two 150 kV and four 450 kV X-ray flashes were used in the impact tests. The numerical simulations were run with the Autodyn code in two steps. In the first, the surface loads were determined for different impact velocities under assumed condition of interface defeat. In the second, these surface loads were applied to the targets in order to obtain critical states of damage and failure related to the transition between interface defeat and penetration, and the corresponding critical velocities. In the impact tests, interface defeat occurred below a transition velocity, which was significantly lower for the conical than for the cylindrical projectiles. Above the transition velocity, the initial penetration of conical projectiles differed markedly from that usually observed for cylindrical projectiles. It occurred along a cone-shaped surface crack, qualitatively corresponding to surface failure observed in the simulations. The transition velocity for the conical projectile was found to be close to the critical velocity associated with this surface failure.
[141] Lundberg P, Westerling L, Lundberg B.1996.

Influence of scale on the penetration of tungsten rods into steel-backed alumina targets

. International Journal of Impact Engineering, 18: 403-416.

DOI      URL      [本文引用: 3]      摘要

As ballistic tests are often performed in reduced geometrical scale, the scaling laws are important for the interpretation of the results. In this study, we tested the validity of replica scaling, by which we mean that all geometrical dimensions are scaled uniformly, while the materials and the impact velocity are kept the same. Long tungsten projectiles with length-to-diameter ratio 15 were fired against unconfined alumina targets with steel backing. The tests were carried out with impact velocities 1500 m sand 2500 m s, and in three different scales with projectile lengths 30, 75 and 150 mm (diameters 2, 5 and 10 mm). The alumina targets were photographed by means of a high-speed camera, and the tungsten projectiles were photographed inside the alumina targets by means of flash radiography. Also, the residual penetrations in the steel backings were measured. The Johnson-Holmquist model for ceramic materials was implemented into the AUTODYN code, which was used for simulation of the experiments. The agreement between results of experiment and simulation was fair, and over the tested interval of scales replica scaling was found to be valid with reasonable accuracy.
[142] Madhu V, Ramanjaneyulu K, Balakrishna Bhat T, Gupta N K.2005.

An experimental study of penetration resistance of ceramic armour subjected to projectile impact

. International Journal of Impact Engineering, 32: 337-350.

DOI      URL      [本文引用: 2]     

[143] Magness L S, Frarand T G.1990.

Deformation behavior and its relationship to the penetration performance of high-velocity KE penetrator material//Proceedings of the 1990 Army Science conference

, Durham: 465-479.

[本文引用: 6]     

[144] Malvar L J, Crawford J E, Wesevich J W, Simons D.1997.

A plasticity concrete material model for DYNA3D

. International Journal of Impact Engineering, 19: 847-873.

DOI      URL      [本文引用: 1]      摘要

Abstract Lagrangian finite element codes with explicit time integration are extensively used for the analysis of structures subjected to explosive loading. Within these codes, numerous material models have been implemented. However, the development of a realistic but efficient concrete material model has proven complex and challenging.The plasticity concrete material model in the Lagrangian finite element code DYNA3D was assessed and enhanced. The main modifications include the implementation of a third, independent yield failure surface; removal of the tensile cutoff and extension of the plasticity model in tension; shift of the pressure cutoff; implementation of a three invariant formulation for the failure surfaces; determination of the triaxial extension to triaxial compression ratio as a function of pressure; shear modulus correction; and implementation of a radial path strain rate enhancement. These modifications insure that the response follows experimental observations for standard uniaxial, biaxial and triaxial tests in both tension and compression, as shown via single element analyses. The radial path strain rate enhancement insures constant enhancement for all those tests. As a full scale example, a standard dividing wall subjected to a blast load is analyzed and the effects of the modifications assessed.
[145] Mcglaun J M, Thompson S L, Elrick M G.1990.

CTH: A three-dimensional shock wave physics code

. International Journal of Impact Engineering, 10: 351-360.

DOI      URL      [本文引用: 3]      摘要

http://linkinghub.elsevier.com/retrieve/pii/0734743X90900713
[146] Mellgrad I, Holmberg L, Olsson G L.1989.

An experimental method to compare the ballistic efficiencies of different ceramics against long rod projectiles//Proceedings of the 11th International Symposium on Ballistics,

Bruseels, Belgium: 323-331.

[本文引用: 1]     

[147] Nia A, Zolfaghari M, Khodarahmi H, Nili M, Gorbankhani A.2014.

High velocity penetration of concrete targets with eroding long- rod projectiles: An experiment and analysis

. International Journal of Protective Structures, 5: 47-64.

DOI      URL      [本文引用: 1]     

[148] Orphal D L.1997.

Phase three penetration

. International Journal of Impact Engineering, 20: 601-616.

DOI      URL      [本文引用: 4]     

[149] Orphal D L.2006.

Explosions and impacts

. International Journal of Impact Engineering, 33: 496-545.

DOI      URL      [本文引用: 7]     

[150] Orphal D L, Anderson Jr. C E.1999.

Streamline reversal in hypervelocity penetration

. International Journal of Impact Engineering, 23: 699-710.

DOI      URL      [本文引用: 2]      摘要

We report a direct observation of the ''streamline'' reversal of eroded rod material proposed by Allen and Rogers in 1961 [1]. Allen and Rogers suggested that the ''turning'' of high-velocity long-rod penetrator material at the target interface could be viewed as a reversal of the direction of a ''streamline'' with only a change of sign in the velocity. Allen and Rogers' streamline reversal model has two important consequences. First, the eroded debris has a speed of v=2u - v relative to the target, where v is the impact velocity and u is the speed of penetration of the rod relative to the target. Secondly, a consequence of v=2u - v is that the length of the rod debris, l, is given by the difference in the initial length of the rod, l, and the remaining length of the rod, l, i.e., l=l- l. Results of a time-resolved experiment for a tungsten penetrator into a polycarbonate target at 3.61 km/s and a corresponding numerical simulation are consistent with streamline reversal. Numerical simulations are then used in a parametric study to investigate the effects of various density ratios between penetrator and target materials.
[151] Orphal D L, Anderson Jr. C E.2006.

The dependence of penetration velocity on impact velocity

. International Journal of Impact Engineering, 33: 546-554.

DOI      URL      [本文引用: 3]      摘要

Recent experimental measurements show that eroding long-rod penetration velocity is a linear function of impact velocity over a very wide range of impact velocities and for an interesting range of rod–target material combinations. These experiments all show that U= a+ bV, where U and V are the penetration and impact velocity, respectively, and “ a” and “ b” are constants for given projectile and target materials. Numerical simulations also show that U= a+ bV. The accumulation of these results suggests that a linear relationship between penetration and impact velocity may be fundamental over a very large range of impact velocities. A linear relationship between penetration and impact velocity has a number of implications. Some implications of this result for the Tate–Alekseevskii model are briefly examined in this paper.
[152] Orphal D L, Anderson Jr. C E, Behner T, Templeton D W.2009.

Failure and penetration response of borosilicate glass during multiple short-rod impact

. International Journal of Impact Engineering, 36: 1173-1181.

DOI      URL      [本文引用: 1]      摘要

In Anderson Jr CE, Orphal DL, Behner T, Templeton, DW [Failure and penetration response of borosilicate glass during short-rod impact. Int J Impact Eng 2009, doi:10.1016/ j.ijimpeng.2008.12.002.] it was demonstrated that the failure front (FF) produced by the penetration of a borosilicate glass target by a gold rod ceased to propagate a short time after the rod was fully eroded. This strongly suggests that progression of the FF is not described by a wave equation. Here it is shown that propagation of the FF is reinitiated if a second co-axial rod, spaced a distance from the first, impacts the glass at the bottom of the penetration channel. The experiments were performed in reverse ballistic mode with two short rods spaced apart. In some experiments both rods were gold; in other experiments, one rod was copper and the other gold. FF propagation was measured using high-speed photography; rod penetration was measured using multiple, independent flash X-rays. Much of the observed phenomenology can be modeled assuming that the rod, either first or second, “communicates” with the FF at a speed corresponding to the bulk sound speed of the undamaged glass.
[153] Orphal D L, Anderson Jr. C E, Franzen R R, Babcock S M.1995.

Variation of crater geometry with projectile $L/D$ for $L/D \leq 1$

. International Journal of Impact Engineering, 17: 595-604.

DOI      URL      [本文引用: 1]      摘要

Abstract A series of hydrocode calculations and terminal ballistics experiments were performed to investigate the penetration mechanics of projectiles with L/D 1. Projectile L/D ranged from 132 to 1; impact velocity ranged from 1.5 to 5 km/s. Projectiles were tungsten or tungsten alloy, targets were RHA. The paper concentrates on the effect of projectile L/D on the size and geometry of the target crater. Normalized crater depth (or penetration) increases with decreasing projectile L/D and achieves a maximum at about LD=18 for 1.5 km/s and 116 for 3 km/s, and then decreases with further decrease in L/D. For 5 km/s, PL increases with decreasing L/D over the entire range studied. PL scales with impact velocity as PL Vf(LD) where, we believe, f(LD) approaches 2 as L/D 0. The ratio of crater to projectile diameter DcD decreases with decreasing L/D and approaches a value of 1 as L/D approaches zero for all velocities studied. The crater shape measured by PDc decreases with decreasing L/D; i.e., as L/D decreases, the crater changes from approximately hemispherical for LD = 1 to a very shallow disk shape. The kinetic energy required per unit crater volume, KEVc, increases with decreasing L/D for LD < 14. That is, cratering efficiency decreases with decreasing projectile L/D. For the impacts studied, KEVc increases from about 5 kJ/cm3 to 12 kJ/cm3 as projectile L/D is reduced from 1 to 132.
[154] Orphal D L, Anderson Jr. C E, Franzen R R, Walker J D, Schneidewind P N, Majerus M E.1993.

Impact and penetration by $L/D\leq 1$ projectiles

. International Journal of Impact Engineering, 14: 551-560.

DOI      URL      [本文引用: 1]      摘要

Calculations of steel target penetration by L/D ≤ 1 tungsten and tungsten alloy projectiles have been extended to ja:math over the velocity range 1.5 to 5 km/s. The ratio of crater to projectile diameter tends to 1 as L/D decreases over this entire velocity range. For impact velocities of 1.5 and 3 km/s, penetration depth normalized by projectile length, P/L, increases with decreasing projectile L/D up to a maximum value and then decreases for still lower L/D. Experiments at impact velocities of 2 and 3 km/s confirm these results. For 5 km/s impact velocity, the calculations show P/L increasing with decreasing projectile L/D over the entire range ja:math . The projectile L/D for which the maximum P/L occurs appears to depend on the impact velocity. P/L generally scales with impact velocity as P/L 65 v f(L/D) where f(L/D) ranges from 0 for a long rod to, we believe, 2 in the limit as projectile L/D approaches zero. The calculations show for ja:math ; for ja:math ; and for ja:math , the new results give P/L 65 v 1.9 .
[155] Orphal D L, Franzen R R.1990.

Penetration mechanics and performance of segmented rods against metal targets

. International Journal of Impact Engineering, 10: 427-438.

DOI      URL      [本文引用: 7]      摘要

Terminal ballistic experiments confirm theoretical predictions that a segmented rod will penetrate a semi-infinite metal target deeper than a continuous rod of the same material and having equal mass, diameter and velocity. For copper segmented rods impacting aluminum targets and tantalum segmented rods impacting 4340 (BHN 300) steel, penetration depths of at least 50 percent greater than that for a corresponding continuous rod are measured at impact velocities of 4 to 5 km/s. Spacing between segments of only about 2.5 segment diameters or more are required to achieve these results. Reducing the Li/D of the segments to less than 1 improves the penetration efficiency of a segmented rod. For segmented rods with segment L i/D < 1, experiments suggest that penetration may increase with impact velocity rate greater than V 2 3.
[156] Orphal D L, Franzen R R.1997.

Penetration of confined silicon carbide targets by tungsten long rods at impact velocities from 1.5 to 4.6km/s

. International Journal of Impact Engineering, 19: 1-13.

DOI      URL     

[157] Orphal D L, Franzen R R, Charters A C, Menna T L, Piekutowski A J.1997.

Penetration of confined boron carbide targets by tungsten long rods at impact velocities from 1.5 to 5.0km/s

. International Journal of Impact Engineering, 19: 15-29.

DOI      URL      [本文引用: 4]      摘要

Forty terminal ballistics experiments were performed to measure the penetration of simple confined boron carbide targets by long tungsten rods. Impact velocities ranged from 1.5 to about 5.0km/s. The experiments were performed in the reverse ballistic mode using a two-stage light-gas gun. For tests with velocities 1.493≤v≤2.767km/s, the penetrator diameter was 1.02mm (0.040inch). For tests with impact velocities v≥2.778km/s the penetrator diameter was 0.762mm (0.030 inch). For tests in the velocity range 2.335 < v< 2.761 km/s both penetrator sizes were used. The length-to-diameter ratio for the penetrator was L/D = 20 for all but the three highest velocity tests; in these three tests L/D = 15. Primary instrumentation for these experiments was four independently timed, 450 kV flash X-rays. These X-rays provided four views of the penetrator-target interaction during the penetration event from which he following data were determined: p = penetration depth as a function of time, L
[158] Orphal D L, Franzen R R, Piekutowski A J, Forrestal M J.1996.

Penetration of confined aluminum nitride targets by tungsten long rods at 1.5-4.5km/s

. International Journal of Impact Engineering, 18: 355-368.

DOI      URL      [本文引用: 2]      摘要

http://linkinghub.elsevier.com/retrieve/pii/0734743X9500045C
[159] Orphal D L, Miller C W.1991.

Penetration performance of nonideal segmented rods

. International Journal of Impact Engineering, 11: 457-461.

DOI      URL      [本文引用: 3]      摘要

Five small scale reverse ballistic tests were performed to examine the effects of a thin-walled surrounding tube and/or lexan spacers between segments on the penetration mechanics and performance of tantalum segmented rods against steel targets. Impact velocity was 4.5–5 km/s. The data, although few, suggest that such structures as surrounding tubes and segment spacers do not necessarily degrade the penetration performance of segmented rods.
[160] Ortiz M.1996.

Computational micromechanics

. Computational Mechanics, 18: 321-338.

DOI      URL      [本文引用: 2]     

[161] Partom Y, Littlefield D L.1995.

Validation and calibration of a lateral confinement model for long-rod penetration at ordnance and high velocities

. International Journal of Impact Engineering, 17: 615-626.

DOI      URL      摘要

In designing targets for laboratory long-rod penetration tests, the question of lateral confinement often arises, How wide should the target be to exert enough confinement? For ceramic targets, the problem is enhanced as ceramics are usually weak in tension and therefore have less self-confinement capability. At high velocities the problem is enhanced even more as the crater radius and the extent of the plastic zone around it are larger. Recently we used the quasistatic cavity expansion model to estimate the resistance of ceramic targets and its dependence on impact velocity [1]. We validated the model by comparing it to computer simulations in which we used the same strength model. Here we use the same approach to address the problem of lateral confinement. We solved the quasistatic cavity expansion problem in a cylinder with a finite outside radius b at which
[162] Piekutowski A J.1996.

Formation and description of debris clouds produced by hypervelocity impact. National Aeronautics and Space Administration

, Marshall Space Flight Center.

[本文引用: 1]     

[163] Piekutowski A J, Forrestal M J, Poormon K L, Warren T L.1999.

Penetration of 6061-T6511 aluminum targets by ogive-nose steel projectiles with striking velocities between 0.5 and 3.0km/s

. International Journal of Impact Engineering, 23: 723-734.

DOI      URL      [本文引用: 1]      摘要

We performed a series of depth-of-penetration experiments using 7.11-mm-diameter, 71.12-mm-long, ogive-nose steel projectiles and 254-mm-diameter, 6061-T6511 aluminum targets. The projectiles were made from vacuum-arc remelted (VAR) 4340 steel (R c 38) and AerMet 100 steel (R c 53), had a nominal mass of 0.021 kg, and were launched using a powder gun or a two-stage, light gas gun to striking velocities between 0.5 and 3.0 km/s. Since the tensile yield strength of AerMet 100 (R c 53) steel is about 1.5 times greater than VAR 4340 (R c 38) steel, we were able to demonstrate the effect of projectile strength on ballistic performance. Post-test radiographs of the targets showed three different regions of penetrator response as the striking velocity increased: (1) the projectiles remained rigid and visibly undeformed; (2) the projectiles deformed during penetration without nose erosion, deviated from the target centerline, and exited the side of the target or turned severely within the target; and (3) the projectiles eroded during penetration and lost mass. To show the effect of projectile strength, we present depth-of-penetration data as a function of striking velocity for both types of steel projectiles at striking velocities ranging from 0.5 and 3.0 km/s. In addition, we show good agreement between the rigid-projectile penetration data and a cavityexpansion model.
[164] Polanco-Loria M, Hopperstad O S, Børvik T, Berstad T.2008.

Numerical predictions of ballistic limits for concrete slabs using a modified version of the HJC concrete model

. International Journal of Impact Engineering, 35: 290-303.

DOI      URL      [本文引用: 1]      摘要

Some modifications to the Holmquist ohnson ook (HJC) model (1993) for concrete under impact loading conditions are proposed. First, the pressure-shear behaviour is enhanced by including the influence of the third deviatoric stress invariant to take into account the substantial shear strength difference between the tensile and compressive meridians. Second, the modelling of strain-rate sensitivity is slightly changed so that the strain-rate enhancement factor goes to unity for zero strain rate. Third, three damage variables describing the tensile cracking, shear cracking and pore compaction mechanisms are introduced. A critical review of the constitutive model with alternative proposals for parameter identification is given. The model parameters are obtained for two concrete qualities, and perforation of concrete slabs is considered numerically and compared with experimental results from the literature. Ballistic limit assessments with deviations under 8% when compared to the experimental results are obtained, indicating that the modified version of the HJC concrete model represents a good compromise between simplicity and accuracy for large-scale computations of concrete plates impacted by projectiles.
[165] Rajendran A M.1994.

Modeling the impact behavior of AD85 ceramic under multiaxial loading

. International Journal of Impact Engineering, 15: 749-768.

DOI      URL      [本文引用: 1]      摘要

This report presents an advanced constitutive model to describe the complex behavior of ceramic materials under impact loading conditions. The governing equations utilize a set of microphysically based constitutive relationships to model deformation and damage processes in a ceramic. The total strain is decomposed into elastic, plastic, and microcracking components. The model parameters for AD85 ceramic were determined using the data from split Hopkinson bar (SHB) and bar-on-bar experiments under uniaxial stress state and plate impact experiment under uniaxial strain state. To further validate the generality of the model parameters, modeling of a diagnostic ballistic experiment in which a steel projectile impacted an AD85 ceramic front-faced thick aluminum plate was considered. In this experiment, stress histories were measured in the target by embedded manganin and carbon stress gauges. The results from the numerical simulations of the ballistic experiment using a shock wave propagation based finite element code successfully matched the measured stress history.
[166] Rajendran A M, Grove D J.1996.

Determination of Rajendran-Grove Ceramic Constitutive Model Constants/

/AIP: 539-542.

DOI      URL      [本文引用: 1]      摘要

This paper presents a methodology to determine the constitutive/damage model constants for silicon carbide for penetration modeling applications. The ceramic constitutive model describes the total strain as the sum of elastic, plastic, and microcracking components. There are effectively nine model constants to be determined. Six constants are adequate to describe the microcracking strain. The pulverized ceramic strength is described through one constant. The plastic strain description involves two which can be determined from a flow stress vs. strain rate plot. By matching the measured velocity vs. time or stress vs. time profiles from plate impact experiments with numerical simulations, the microcracking model constants can be determined. The fracture toughness value is available in material handbooks. In a two dimensional hydrocode analysis, the pulverized ceramic strength model parameter is adjusted to match the measured depth of penetration in a ballistic test.
[167] Reaugh J E, Holt A C, Welkins M L, Cunningham B J, Hord B L, Kusubov A S.1999.

Impact studies of five ceramic materials and pyrex

. International Journal of Impact Engineering, 23: 771-782.

DOI      URL      [本文引用: 1]      摘要

http://linkinghub.elsevier.com/retrieve/pii/S0734743X99001219
[168] Rong G, Huang D W, Yang M C.2012.

Penetrating behaviors of Zr-based metallic glass composite rods reinforced by tungsten fibers

. Theoretical and Applied Fracture Mechanics, 58: 21-27.

DOI      URL      [本文引用: 1]      摘要

Ballistic tests are performed by shooting both tungsten fiber/bulk metallic glass W/Zr58Ti13Cu17Ni12 composite rods (composite rod) and tungsten heavy alloy rods (95W rod) into 30CrMnMo target. The composite rod exhibits self-sharpening behaviors, and its matrix damages and fibers break are limited in a thin, narrow area, which is defined as “edge layer”. Penetrating depth of composite rods is 50% deeper than the depth of 95W rods with same dimension size.
[169] Rosenberg Z.1993.

On the relation between the Hugoniot elastic limit and the yield strength of brittle materials

. Journal of Applied Physics, 1: 752-753.

[本文引用: 1]     

[170] Rosenberg Z, Ashuach Y, Dekel E.2007.

More on the ricochet of eroding long rods—validating the analytical model with 3D simulations

. International Journal of Impact Engineering, 34: 942-957.

DOI      URL      [本文引用: 1]      摘要

The ricochet of eroding long rods, from inclined steel targets, is investigated by a series of three-dimensional (3D) numerical simulations. These are compared with the predictions of our, previously published, analytical model for ricochet. The agreement between simulation results and model predictions is excellent, strongly enhancing our simple ricochet model. We also highlight several aspects of our model which are derived from its simple closed form. One of these is the fact that ricochet of long rods can take place only at velocities and obliquities which are higher than certain threshold values. Otherwise, the process involves rod bending and sliding along the target impact face.
[171] Rosenberg Z, Ashuach Y, Yeshurun Y, Dekel E.2009.

On the main mechanisms for defeating AP projectiles, long rods and shaped charge jets

. International Journal of Impact Engineering, 36: 588-596.

DOI      URL      [本文引用: 2]      摘要

Some of the important mechanisms for defeating various projectiles and shaped charge are reviewed in this paper. These mechanisms are based on the compressive strength of the target material (its inherent resistance to penetration) and on the asymmetrical forces which it exerts on the threat, through proper geometrical arrangements. We discuss the basic features of the resistance to penetration, starting with the classical analysis of the cavity expansion process in elasto-plastic solids. This property of the target is responsible for the deceleration of hard cored projectiles and for the erosion of long rods, under normal impact conditions. We then discuss the asymmetrical interaction of armor piercing (AP) projectiles, long rods and shaped charge jets with inclined plates (stationary and moving). These asymmetric forces, exerted on the impacting threat, are responsible for their deflection and breakup. Our work combines experimental observations with numerical simulations and engineering models, which highlight the basic mechanisms behind these complex situations. This understanding is necessary for optimizing the performance of any armor design against a given threat.
[172] Rosenberg Z, Dekel E.1994a.

The relation between the penetration capability of long rods and their length to diameter ratio

. International Journal of Impact Engineering, 15: 125-129.

DOI      URL      [本文引用: 8]      摘要

Recent experimental studies, on the penetration of long rods into semi-infinite steel targets, reveal some features which cannot be predicted by the conventional 1-D penetration model of Alekseevskii and Tate. This paper presents experimental results together with 2-D simulations which were performed in order to investigate this discrepancy. Specifically we are interested in the question of whether the normalized penetration curve—P/L (P is penetration depth, L is penetrator length)—is dependent on penetrator's length to diameter ratio in the range of L/D = 10–40. Both experimental and simulation results show a decrease of about 15% between P/L values for L/D = 10 and 20 rods as well as for L/D = 20 and 30. These, rather large, differences are discussed in terms of material parameters which are resonsible for the discrepancy between the 1-D model and both experiment and simulation. Moreover, we have simulated the penetration of long rods having zero yield strength. Our results show that for large aspect ratios (L/D > 30) these weaker rods penetrate more than those with their full yield strength. This crossover phenomenon is both counterintuitive as well as opposed to the predictions of the 1-D model for this combination of rod-target materials.
[173] Rosenberg Z, Dekel E.1994b.

A critical examination of the modified Bernoulli equation using two-dimensional simulations of long rod penetrators

. International Journal of Impact Engineering, 15: 711-720.

DOI      URL      [本文引用: 5]      摘要

Abstract The modified Bernoulli equation is examined through a series of two-dimensional simulations of long rods penetrating semi-infinite targets. These are copper, aluminium and tungsten alloy rods having zero strength with length-to-diameter ratios of 20. The targets are steel and tungsten alloy with yield strengths in the range of 0 2 GPa. Impact velocities were varied between 1 and 7 km/s. Each simulation results in a definite value for the steady-state penetration velocity, which is substituted in the modified Bernoulli equation to derive an effective resistance to penetration (Rt). The dependence of Rt on target yield strength, impact velocity and projectile and target characteristics is determined.
[174] Rosenberg Z, Dekel E.1996.

A computational study of the influence of projectile strength on the performance of long-rod penetrators

. International Journal of Impact Engineering, 18: 671-677.

DOI      URL      [本文引用: 6]      摘要

Two-dimensional numerical simulations were used to explore the penetration capability of long-rods as a function of their strength. Tungsten alloy rods of varying strengths were ‘shot’ at semi-infinite armor steel targets in the velocity range of 1.4–2.2 km/s. It is found that penetration depths versus penetrator strength curves have a maximum which depends on the impact velocity. This effect which, to our best knowledge, has not been reported previously can be explained, at least qualitatively, by considering the deceleration of the rear part of the rod, as its strength increases. This deceleration can lead to a substantial decrease in the velocity of the rear part of the penetrator with the result that its penetration capability is reduced beyond that of a nondecelerating penetrator. The deceleration is a direct consequence of the elastic waves travelling along the back part of the rod with an amplitude which is equal to the strength of the penetrator material.
[175] Rosenberg Z, Dekel E.1998.

A computational study of the relations between material properties of long-rod penetrators and their ballistic performance

. International Journal of Impact Engineering, 21: 283-296.

DOI      URL      [本文引用: 7]      摘要

The paper summarizes a series of two-dimensional numerical simulations which were performed to study the effects of material properties on the terminal ballistics of long-rod penetrators. Our focus was on the properties of the rod material, unlike recent works which concentrated on a target properties. We varied almost all the relevant parameters within a large range of values in order to study the separate effects of each one. These parameters included: compressive and tensile strengths, elastic moduli, melting temperatures and the maximum equivalent plastic strain (failure strain) of the rod material. Most of the simulations were performed for an actual experiment with 300 mm tungsten-alloy long-rod, impacting a semi-infinite steel target. The simulations show that the mechanical and thermal softening mechanisms are the most dominant, as far as the depth of penetration is concerned. In contrast, the elastic moduli and spall strength have a negligible effect as far as penetration depth is concerned.
[176] Rosenberg Z, Dekel E.1999.

On the role of nose profile in long-rod penetration

. International Journal of Impact Engineering, 22: 551-557.

DOI      URL      [本文引用: 7]      摘要

The superiority of depleted uranium on tungsten-alloy penetrators has recently been assigned to the self-sharpening mechanism, at the tip of the DU rods, due to the adiabatic shear failure which this material experiences. The purpose of the work presented here was to further investigate the role of deformed nose profile on the deep penetrations of long rods into semi-infinite targets. This was achieved through a series of 2-D numerical simulations and several perforation experiments where we recovered and examined the residual penetrators. The simulations were performed for rigid tungsten-alloy rods having five different nose shapes with the density and elastic properties of tungsten alloys. For the normal impact experiments we chose three rod materials: a tungsten alloy, a copper and a titanium alloy. The residual rods (after perforation of finite thickness targets) were imaged by flash X-ray and softly recovered using sand boxes. As expected, the nose shapes of these rods were very different from each other.
[177] Rosenberg Z, Dekel E.2000.

Further examination of long rod penetration: the role of penetrator strength at hypervelocity impacts

. International Journal of Impact Engineering, 24: 85-102.

DOI      URL      [本文引用: 11]      摘要

2D numerical simulations were performed in order to further investigate the role of penetrator strength in the interaction of long rods and semi-infinite targets. These simulations are used to highlight the reasons for several discrepancies between existing data and the well-known 1D model for penetration. In particular, the nature of the secondary penetration of high-density rods, the hydrodynamic limits of high-strength rods, and the predicted maxima in their penetration curves are discussed. The causes for these discrepancies are established by additional numerical simulations which explore the validity of the penetrator strength parameter in the analytical model as a physical entity. It is shown that this is, indeed, the weakest part of the model since it is strongly dependent on both the impact velocity of the rod and its length-to-diameter ratio.
[178] Rosenberg Z, Dekel E.2001a.

More on the secondary penetration of long rods

. International Journal of Impact Engineering, 26: 639-649.

DOI      URL      [本文引用: 5]      摘要

The secondary penetration of long rods, impacting semi-infinite metallic targets, has been investigated since the early 60's, both experimentally and analytically. Several models have been proposed for the extra penetration which is achieved by these rods at the later stages of the process. However, the models are of limited applicability since they cover only limited regimes of the relevant parameters. In order to further understand the phenomenon of secondary penetration, we performed a large number of numerical simulations using the PISCES 2 DELK code. These simulations dealt with the relevant parameters in large ranges of variability, such as: the rod impact velocity, its aspect ratio (L/D), as well as the densities and strengths of rod and target material. We show that the semi-empirical formulations do not account for the whole range of these parameters. Our simulations show that the strength of the rod has a major influence on the values of the secondary penetrations. In addition, these values are strongly dependent on L/D and target strength.
[179] Rosenberg Z, Dekel E.2001b.

Material similarities in long-rod penetration mechanics

. International Journal of Impact Engineering, 25: 361-372.

DOI      URL      [本文引用: 2]      摘要

The process of long-rod penetration into thick metallic targets is examined through a series of two-dimensional simulations. The aim of the research presented here is to uncover the inherent material similarities in this process. In particular, the search is for non-dimensional parameters which account for the depth of penetration, such as the density ratio, and the relative strengths of penetrator and target. The simulation results are in accord with existing empirical data, shedding more light on the penetration process and emphasizing the difficulties in achieving an overall normalization procedure for this process.
[180] Rosenberg Z, Dekel E.2003.

Numerical study of the transition from rigid to eroding-rod penetration

. Journal De Physique IV, 110: 681-686.

DOI      URL      [本文引用: 3]      摘要

The behavior of rigid long rods, during deep penetration into thick metallic targets, is quite different from that of eroding rods. These differences are discussed in the present paper, through a series of 2D numerical simulations, compared with experimental data, on steel rods impacting aluminum targets. Special emphasis is placed on the threshold impact velocity, where the rods are starting to deform. At these velocities, penetration depths of the rods decrease substantially, and we were trying to account for these reductions in our simulations. We also study the effect of rod aspect ratio (L/D) on its penetration efficiency (P/L), as well as the role of rod and target strengths and their density ratio ( _p/ _t) on this efficiency.
[181] Rosenberg Z, Dekel E.2004.

On the role of material properties in the terminal ballistics of long rods

. International Journal of Impact Engineering, 30: 835-851.

DOI      URL      [本文引用: 9]      摘要

The terminal ballistics of long-rod penetrators is a very complex field of research involving high pressure physics, continuum mechanics, material science and high strain rate phenomena. The research in this field is advanced through experimental data collection, engineering models, and numerical simulations. In the present paper, we summarize some of our recent work which is focused on determining the important material parameters in the interaction of long rods with various targets (both stationary and moving). Our basic goal is to be able to account for various phenomena encountered in the experiments, rather than reproduce the data very accurately. We achieve this goal by using the minimal set of material parameters which is needed in order to highlight the basic features in the interaction. We also show how 3D numerical simulations help to establish a simple model for the complex interaction between a tungsten alloy rod and a moving steel plate.
[182] Rosenberg Z, Dekel E.2008.

A numerical study of the cavity expansion process and its application to long-rod penetration mechanics

. International Journal of Impact Engineering, 35: 147-154.

DOI      URL      [本文引用: 2]      摘要

The paper describes a series of 2D numerical simulations which followed the cavity expansion process in an elasto- plastic solid. The results from these simulations, in terms of cavity wall motion as a function of the applied pressures inside the cavity, highlighted several issues concerning cavity expansion process and the terminal ballistics of both rigid and eroding long rods. These issues include the form of the relation between the dynamic radial stress on the cavity wall and its velocity, which can be written in a simple, normalized form, at least for the materials we simulated here. Also, the difference between target resistance to the penetration of rigid and eroding-rod penetration, was quantified with a series of simulations in which the pressures in the cavity were applied on an angular section, rather than on its whole surface. Finally, we explored the inherent differences between spherical and cylindrical cavity expansion processes, which can be helpful for analytical models of the penetration of rigid rods with different nose shapes.
[183] Rosenberg Z, Dekel E.2010.

On the deep penetration of deforming long rods

. International Journal of Solids & Structures, 47: 238-250.

DOI      URL      [本文引用: 1]      摘要

A series of 2D numerical simulations was performed in order to follow various features in the penetration mechanics of deforming long rods. In particular, we were interested in the threshold velocity which marks the transition from rigid to deforming rod and the resulting depths of penetration around this transition velocity. We simulated various cases in which we varied the yield strengths of the rod and the target, as well as their densities and the nose shape of the rod. With the results of these simulations we constructed a rather simple model which accounts for the threshold velocity from rigid to deforming rod behavior. This model predictions are in good agreement with both our simulations and with experimental data for various rods and targets.
[184] Rosenberg Z, Dekel E.2012.

Terminal Ballistics. Springer Berlin Heidelberg

.

[本文引用: 7]     

[185] Rosenberg Z, Dekel E, Ashuach Y.2006.

More on the penetration of yawed rods

. Journal De Physique IV, 134: 397-402.

DOI      URL      [本文引用: 2]      摘要

One of the most complex processes, in the field of terminal ballistics, is that of yawed impact of long rods. In spite of many experimental observations, and some analytical modeling, a clear picture of this issue is still lacking. In order to gain some insight into the operating mechanisms, we developed a simple engineering model which considers the yawed rod as a series of small disks. We then define the effective length and diameter of the rod by considering those disks which are going to hit the initial crater which is opened by the impact. We also performed a series of 3D numerical simulations with various L/D tungsten alloy rods impacting a steel target, at yaws in the full range of 0-90^circ. We analyzed the results of these simulations in terms of the normalized penetration (P/D), where D is the rod diameter, and looked for systematic trends in the results for the various rods. The agreement between our model predictions and both experimental data and simulation results is quite good. Based on this agreement we can highlight some new features of the penetration process of yawed rods.
[186] Rosenberg Z, Dekel E, Hohler V, Stilp A J, Weber K.1997a.

Hypervelocity penetration of tungsten alloy rods into ceramic tiles: experiments and 2-D simulations

. International Journal of Impact Engineering, 20: 675-683.

DOI      URL      [本文引用: 4]      摘要

A series of terminal ballistics experiments and 2-D simulations, with small scale tungsten alloy penetrators, was performed in order to quantify the ballistic efficiency of confined ceramic tiles. The data includes both depth of penetration (DOP), into thick steel backing and X-ray shadowgraphs during the penetration process. Impact velocities ranged between 1.25 to 3.0 km/s. The size of the tiles varied in order to check their performance as a function of thickness and lateral dimensions. We found that the differential ballistic efficiency of alumina tiles is practically independent on impact velocity and tile thickness, within the ranges of velocity and thicknesses, investigated here. A detailed simulation study, using the Eulerian processor of the PISCES 2-D ELK code, was performed in order to better understand the interaction between long-rods and ceramic tiles, and particularly, to adjust a proper failure criterion to the tiles. We found that a simple version of the Johnson-Holmquist model, with a single parameter, is fairly adequate to account for most of the data. These include: lateral confinement, tile thickness and impact velocity influence on the penetration depth. We used the code to further investigate the influence of lateral dimensions on tile performance.
[187] Rosenberg Z, Dekel E, Hohler V, Stilp A J, Weber K.1998.

Penetration of Tungsten-Alloy rods into composite ceramic targets: Experiments and 2-D Simulations//Proceedings of the APS conference on Shock Waves in Condensed Matter

, Amherst, Mass: 917-920.

[本文引用: 4]     

[188] Rosenberg Z, Dekel E, Yeshurun Y, Bar-On E.1995.

Experiments and 2-D simulations of high velocity penetrations into ceramic tiles

. International Journal of Impact Engineering, 17: 697-706.

DOI      URL      [本文引用: 3]      摘要

This paper investigates the interaction of long-rod penetrators with thick ceramic tiles, sandwiched between steel plates, through several model experiments and 2-D simulations. Experimental data from low velocity penetrations have been used to calibrate the relevant properties of the ceramic specimens. The influence of increasing impact velocity on tile performance was then investigated through data and simulations of shaped charge jets penetrating the ceramic. We found that the ballistic efficiency of the ceramic tile is lower against high velocity (5 km/s) long-rods, in contrast with the common thesis that their improved performance against shaped charge jets is the result of their enhanced strength. On the other hand, our simulations clearly show that, for high strength ceramics, there is a radial motion of metal and ceramic debris towards the penetration axis. This effect is, probably, the main reason for the considerable improvement in the performance of ceramic tiles against shaped charge jets.
[189] Rosenberg Z, Kreif R, Dekel E.1997b.

A note on the geometric scaling of long-rod penetration

. International Journal of Impact Engineering, 19: 277-283.

DOI      URL      [本文引用: 2]      摘要

The paper describes a set of experiments with copper and tungsten alloy long-rods, which were aimed at finding the sources of non-scaling effects recently discovered in terminal ballistics. Our basic assumption was that geometrical scaling should hold for ductile penetrators (like copper) and that any deviation from this scaling should be attributed to brittle failure mechanisms at the penetrator's head. Our experimental results support this assumption as far as the depth of penetration into steel of two penetrators, differing by a factor of 2, is considered. Thus, copper penetrators scaled well, within experimental error, while a difference of about 10% was found between the depth of penetration of 1:2 and 1:4 tungsten alloy penetrators. We also present two-dimensional simulations, which were performed with the PISCES 2DELK code, in order to determine lateral edge effects. These simulations enabled us to choose the right size for our “infinite” targets, avoiding any influence from their lateral-free surface.
[190] Rosenberg Z, Marmor E, Mayseless M.1990.

On the hydrodynamic theory of long-rod penetration

. International Journal of Impact Engineering, 10: 483-486.

DOI      URL      [本文引用: 5]      摘要

The hydrodynamic theory of long-rod penetration is reexamined by applying the modified Bernoulli equation to the forces acting on both sides of the moving rod-target interface. Using a ratio of 2 for the effective cross sectional areas of the mushroomed and rigid parts of the rod, it is shown that analytical expressions can be used to calculate the resistance to target penetration. The analytical expression used to calculate this resistance is the cylindrical cavity expansion, which yields resistance values of 3 4 times the compressive yield strength of the target material. Calculations based on our model show good agreement with experimental data, for steel and tungsten long rods penetrating various steel targets.
[191] Rosenberg Z, Tsaliah J.1990.

Applying Tate's model for the interaction of long rod projectiles with ceramic targets

. International Journal of Impact Engineering, 9: 247-251.

DOI      URL      [本文引用: 2]      摘要

The penetration of ceramic tiles by long rod penetrators is discussed in terms of the modified hydrodynamic theory of A. Tate which was developed for thick metallic targets. The resistance of the tile to penetration is determined with the threshold velocity for the penetration of a very large ceramic block. According to Tate's theory, the threshold impact velocity for a given projectile (with a well defined strength) depends only on the tile's resistance to penetration. We show here that using three different projectiles (copper, steel and tungsten) resulted in the same value for this parameter for thick alumina tiles. This fact strongly enhances the idea of applying Tate's theory to ceramics. A different set of experiments, with relatively thin tiles bonded to thick steel plates, was performed determining penetration depths of the long rods into the steel backing. These were compared with predictions based on Tate's model using the values for the penetration resistance, which were determined by thick tile experiments. The good agreement can be considered as a further confirmation of our main thesis. Resistance of penetration parameters ( R t) were determined for other ceramics (silicon carbide, titanium diboride, etc.) by measuring the penetration depths of the long rod projectile into the thick backing and using Tate's model with R t as a parameter.
[192] Rosenberg Z, Yeshurun Y, Mayseless M.1989.

On the ricochet of long rod projectiles//Proceedings of the 11th international symposium on ballistics

, Brussels: 501-506.

[本文引用: 4]     

[193] Rozenberg Z, Yeshurun Y.1988.

The relation between ballastic efficiency and compressive strength of ceramic tiles

. International Journal of Impact Engineering, 7: 357-362.

DOI      URL      摘要

Ballistic tests with armor piercing projectiles on different ceramic tiles are presented. The tests were conducted using the thick-backing configuration, which is a new experimental technique to evaluate ballistic efficiencies of ceramic tiles. The residual penetration of the projectile into a thick metallic backing plate, which supports the ceramic tile, is measured. It is shown that the ballistic efficiencies of the different tiles increase monotonically with their normalized effective strength. This strength parameter is defined as the average of the static and dynamic compressive strengths divided by the density of the ceramic. A simple analysis is presented which accounts for the linear dependence of the ballistic efficiency on the normalized effective strength.
[194] Sadanandan S, Hetherington J G.1997.

Characterisation of ceramic/steel and ceramic/aluminium armours subjected to oblique impact

. International Journal of Impact Engineering, 19: 811-819.

DOI      URL      [本文引用: 1]      摘要

This paper investigates the performance of alumina/5083 aluminium, and alumina/Grade 43A steel armours when subjected to oblique impact by 7.62 mm Swedish FFV Armour Piercing, and U.K. Ball ammunition. It also describes the failure mechanism of composite targets and highlights the differences in Ball and AP attacks. It was found that the ballistic limit velocity ( V 50 ) increased with obliquity. In the majority of cases a weight penalty was incurred when such armour was inclined to attack. The results obtained were compared with predictions from both theoretical and empirical models and showed reasonable correlation. The theoretical model is based on an assumed failure mechanism which describes the observed deformation patterns. The empirical relationships are based on root cosine and root secant expressions [i.e. (AD(06)AD(n) = cos0.5 06), and (V50(θ)V50(n) = sec0.5 06)] and provide an effective tool in armour design.
[195] Satapathy S.2001.

Dynamic spherical cavity expansion in brittle ceramics

. International Journal of Solids & Structures, 38: 5833-5845.

DOI      URL      [本文引用: 2]      摘要

In this paper we derived the pressure required to open a spherical cavity in an infinite brittle ceramic at a constant speed. The ceramic material is assumed to crack upon reaching its elastic limit. Subsequent failure of the cracked material due to compressive failure renders pulverization of the material. The pulverized material is assumed to follow a Mohr oulomb type constitutive behavior. The results show that at high cavity expansion speeds the comminuted region outruns the cracked region, i.e. the cracked region disappears. At very high cavity expansion speeds the comminuted zone propagation speed saturates at a level slightly below the longitudinal wave speed. Limited comparison with experimental penetration resistance shows reasonable agreement between theory and experiment.
[196] Satapathy S S, Bless S J.2000.

Cavity expansion resistance of brittle materials obeying a two-curve pressure--shear behavior

. Journal of Applied Physics, 88: 4004-4012.

DOI      URL      [本文引用: 1]      摘要

We derived a closed-form solution for the pressure required to open a spherical or a cylindrical cavity in brittle materials which demonstrate a two-curve pressure hear behavior. The material is allowed to crack under tension and fail under shear; only both failure modes result in comminution. Since the cavity expansion pressure is closely related to the penetration resistance of a target material, this solution identifies the material parameters that are important in impact and penetration problems. It is found that cracking and comminution can be prevented when a large enough confinement pressure is present, and the resulting high cavity expansion resistance could explain the intriguing phenomenon of interface defeat. The effects of dilatancy, and shear strength of comminuted ceramic on cavity expansion pressure are explicitly revealed.
[197] Segletes S B, Walters W P.2003.

Extensions to the exact solution of the long-rod penetration/erosion equations

. International Journal of Impact Engineering, 28: 363-376.

DOI      URL      [本文引用: 1]      摘要

The exact solution to the long-rod penetration equations is revisited, in search of improvements to the solution efficiency, while simultaneously enhancing the understanding of the physical parameters that drive the solution. Substantial improvements are offered in these areas. The presentation of the solution is simplified in a way that more tightly unifies the special- and general-case solutions to the problem. Added computational efficiencies are obtained by expressing the general-case solution for penetration and implicit time in terms of a series of Bessel functions. Other extensions and efficiencies are addressed, as well.
[198] Senf H, Rothenhausler H, Scharpf F, Both A, Pfang W.1981.

Experimental and numerical investigation of the ricocheting of projectiles from metallic surfaces//Proceedings of the 6th international symposium on ballistics

, Orlando: 510-521.

[本文引用: 1]     

[199] Shin H, Yoo Y.2003.

Effect of the velocity of a single flying plate on the protection capability against obliquely impacting long-rod penetrators

. Combustion, Explosion, and Shock Waves, 39: 591-600.

DOI      URL      摘要

The protection capability of a flying steel plate against obliquely impacting tungsten heavy alloy long‐rod penetrators was simulated using the NET3D code as a function of plate velocity ranging from 610.5 to 0.5 km/sec at an obliquity of 60°. The negativity in plate velocity was assigned if the plate had a velocity component in the direction of penetrator progress. Based on the residual kinetic energy of the penetrator after perforating the plate, the protection capability of the plate increased as the plate velocity decreased to a negative value at both a normal ordnance velocity (1.5 km/sec) and a hypervelocity (2.5 km/sec) impact. The defeat capability of the oblique plate increased as the impact velocity increased in the plate velocity range studied in this work. The interaction mechanisms between the penetrator and steel plate, responsible for these results, were investigated. The physical meaning of the results obtained in this work were discussed in the light of sensor‐activated and reactive armours.
[200] Silsby G F.1984.

Penetration of semi-infinite steel targets by tungsten rods at 1.3 to 4.5km/s//Proceedings of the 8th International Symposium on

Ballistics.

[201] Silsby G F, Roszak R J, Giglio-Tos L.1983.

BRL's 50mm high pressure powder gun for terminal ballistic testing-the first year's experience

. Ballistic Research Laboratory Report No. BRL-MR-03236.

[本文引用: 2]     

[202] Song W J, Chen X W, Chen P.2017a.

A simplified approximate model of compressible hypervelocity penetration

. Acta Mechanica Sinica, doi:10.1007/s10409-018-0769-9.

DOI      URL      [本文引用: 1]      摘要

A simplified approximate model considering rod/target material's compressibility is proposed for hypervelocity penetration. We study the effect of shockwaves on hypervelocity penetration whenever the compressibility of the rod is much larger, analogously, and much less than that of the target, respectively. The results show that the effect of shockwaves is insignificant up to 12 km/s, so the shockwave is neglected in the present approximate model. The Murnaghan equation of state is adopted to simulate the material behaviors in penetration and its validity is proved. The approximate model is finally reduced to an equation depending only on the penetration velocity and a simple approximate solution is achieved. The solution of the approximate model is in agreement with the result of the complete compressible model. In addition, the effect of shockwaves on hypervelocity penetration is shown to weaken material's compressibility and reduce the interface pressure of the rod/target, and thus the striking/protective performance of the rod/target is weakened, respectively. We also conduct an error analysis of the interface pressure and penetration efficiency. With a velocity change of 1.6 times the initial sound speed for the rod or target, the error of the approximate model is very small. For metallic rod-target combinations, the approximate model is applicable even at an impact velocity of 12 km/s.
[203] Song W J, Chen X W, Chen P.

2017b. The effects of compressibility and strength on penetration of long rod and jet

. Defence Technology, 2017, DOI: 10.1016/j.dt.2017.11.010.

DOI      URL      [本文引用: 1]     

[204] Song W J, Chen X W, Chen P.2018.

Effect of compressibility on the hypervelocity penetration

. Acta Mechanica Sinica, 34: 82-98.

DOI      URL      [本文引用: 1]      摘要

We further consider the effect of rod strength by employing the compressible penetration model to study the effect of compressibility on hypervelocity penetration. Meanwhile, we define different instances of penetration efficiency in various modified models and compare these penetration efficiencies to identify the effects of different factors in the compressible model. To systematically discuss the effect of compressibility in different metallic rod-target combinations, we construct three cases, i.e., the penetrations by the more compressible rod into the less compressible target, rod into the analogously compressible target, and the less compressible rod into the more compressible target. The effects of volumetric strain, internal energy, and strength on the penetration efficiency are analyzed simultaneously. It indicates that the compressibility of the rod and target increases the pressure at the rod/target interface. The more compressible rod/target has larger volumetric strain and higher internal energy. Both the larger volumetric strain and higher strength enhance the penetration or anti-penetration ability. On the other hand, the higher internal energy weakens the penetration or anti-penetration ability. The two trends conflict, but the volumetric strain dominates in the variation of the penetration efficiency, which would not approach the hydrodynamic limit if the rod and target are not analogously compressible. However, if the compressibility of the rod and target is analogous, it has little effect on the penetration efficiency.
[205] Sorensen B R, Kimsey K D, Silsby G F, Scheffler D R, Sherrick T M, de Rosset W S.1991.

High velocity penetration of steel targets

. International Journal of Impact Engineering, 11: 107-119.

DOI      URL      [本文引用: 5]      摘要

Researchers at the U.S. Army Ballistic Research Laboratory (BRL) have conducted a combined experimental and numerical research program in high-velocity penetration aimed at increasing the understanding of penetration mechanics over the striking velocity range between 1.5 and 4 km/s. A judicious combination of ballistic tests and large-scale simulations have been used to evaluate the performance of a family of both monolithic and segmented penetrators against semi-infinite rolled homogeneous armor (RHA). The results of the experimental and numerical programs are discussed.
[206] Steinberg D J.1987.

Constitutive model used in computer simulation of time-resolved, shock-wave data

. International Journal of Impact Engineering, 5: 603-611.

DOI      URL      [本文引用: 2]      摘要

We have designed a constitutive model for use with high-speed, hydrodynamic computer codes. The model, valid at high-deformation rates, accounts for pressure and temperature dependence of the yield strength and shear modulus, work hardening, pressure-dependent melting, Bauschinger and strain-rate effects, and spall. There are a minimum number of parameters needed to implement the model, and most can be determined without recourse to shock-wave data. At Lawrence Livermore National Laboratory, we assembled a library of these material properties for 44 metals, alloys, mixtures, and compounds. Shock and release data from plate-impact experiments for Be, U, Ta, Cu, 1100-0, and 6061-T6 Al, with peak stresses from 6.4 to 230 GPa, are successfully compared against calculations.
[207] Steinberg D J, Cochran S G, Guinan M W.1980.

A constitutive model for metals applicable at high-strain rate

. Journal of Applied Physics, 51: 1498-1504.

DOI      URL      [本文引用: 1]      摘要

A model, applicable at high‐strain rate, is presented for the shear modulus and yield strength as functions of equivalent plastic strain, pressure, and internal energy (temperature). The parameters needed to implement the model have been determined for 14 metals. Using this model, hydrodynamic computer simulations have been successful in reproducing measured stress and free‐surface‐velocity–vs–time data for a number of shock‐wave experiments.
[208] Steinberg D J, Lund C M.1989.

A constitutive model for strain rates from 0.0001 to 1,000,000/s

. Journal of Applied Physics, 65: 1528-1533.

DOI      URL      [本文引用: 1]     

[209] Sternberg J.1989.

Material properties determining the resistance of ceramics to high velocity penetration

. Journal of Applied Physics, 65: 3417-3424.

DOI      URL      摘要

The relationships between target material properties and the target strength term in the analytic representation of impact is examined. For ductile materials hardness is closely related to the magnitude of the strength term. It is shown that the key parameters correlating microhardness measurements in ceramics are similar to those for ductile materials. However, the strength terms that have been measured in ballistic tests are much lower than the values that would be predicted on the basis of the indentation measurements. It is found that the penetration resistance depends on the fracture toughness, where the ratio of the measured target strength term to the hardness increases with the fracture toughness of the target.
[210] Stilp A J, Hohler V.1990.

Experimental methods for terminal ballistics and impact physics//High Velocity Impact Dynamics

. Wiley, New York :515-592.

[本文引用: 2]     

[211] Stilp A J, Hohler V.1995.

Aeroballistic and impact physics research at EMI-an historical overview

. International Journal of Impact Engineering, 17: 785-805.

DOI      URL      [本文引用: 1]      摘要

On the occasion of the Distinguished Scientist Award presentation at HVIS 1992, the technical and scientific promotion of the Impact Physics Division at EMI in the field of aeroballistics, free flight dynamics, terminal ballistics and impact physics is described. This development is closely related to the work of the recipients. The activities began in the late fifties when a small pressurized ballistic range with a gas gun was built. The problems to construct a well working facility with observation stations are reported that arose, at those early times, from the lack of experience, money and suitable locations. In the mid-sixties, the experimental possibilities were extended by building a two-stage light gas gun that could also be used as a gun tunnel. These facilities have been the foundation for research in the field of free flight aerodynamics, such as the study of near and far wakes behind a blunt hypersonic body or the study of shock wave boundary layer interactions. In 1972, th e division took the first step into terminal ballistics and, because of increasing interest, impact physics became the main research area. The division grew and with it the instrumentation. Today, diverse gas guns, powder guns and two-stage light gas guns are in operation. One topic of main interest during the years has been the penetration of rod shaped projectiles. Here the best-known result may be mentioned, the so-called 'Hohler-Stilp S-shaped penetration curves`. In addition to this, many other topics have been investigated that can be summarized under the title "penetration mechanics and impact physics". Based on a well developed launching technique and instrumentation, problems were investigated at low velocities of a few hundred m/s, at ordnance velocities and especially at hypervelocities up to 10 km/s. It has been recognized that dynamic material behavior and microstructural effects play an important role in understanding the interaction of projectiles with targets. Therefore , a VISAR, an electronic raster microscope, a Hopkinson bar and further equipment have been installed. Basing on the work of a period of more than 20 years, EMI has come into contact with national and foreign institutions and has become a partner for many cooperations.
[212] Subramanian R, Bless S J.1995.

Penetration of semi-infinite AD995 alumina targets by tungsten long rod penetrators from 1.5 to 3.5km/s

. International Journal of Impact Engineering, 17: 807-816.

DOI      URL      [本文引用: 3]      摘要

In tests in which the ratio of target diameter to penetrator diameter was reduced to 15, R t , dropped by 30% to 50%. When a steel coverplate was used, total interface defeat occurred at 1.5 km/s.
[213] Subramanian R, Bless S J, Cazamias J, Berry D.1995.

Reverse impact experiments against tungsten rods and results for aluminum penetration between 1.5 and 4.2km/s

. International Journal of Impact Engineering, 17: 817-824.

DOI      URL      [本文引用: 5]      摘要

Reverse impact experiments against 0.76 mm diameter L/D = 20 tungsten rods have been conducted with a 38 mm diameter launch tube, two-stage light-gas gun using four 450 kV flash X-rays to measure penetration rates. Techniques for projectile construction, sample placement, alignment, and radiography are described. Data for penetration rate, consumption velocity, and total penetration were obtained for 28 mm diameter 6061-T651 aluminum cylinders at impact velocities between 1.5 and 4.2 km/s. It was found that penetration velocity was a linear function of impact velocity over this velocity range. Above 2 km/s impact velocity, penetration was completely hydrodynamic. There was substantial secondary penetration, and the total penetration increased linearly with impact velocity over the range 1.5 to 2.5 km/s.
[214] Tate A.1967.

A theory for the deceleration of long rods after impact

. Journal of the Mechanics & Physics of Solids, 15: 387-399.

DOI      URL      [本文引用: 4]      摘要

A modified hydrodynamic theory which takes some account of strength effects is used to predict the deceleration of a long rod after striking a target. The results are then compared with experimental data from X-ray observations.
[215] Tate A.1969.

Further Results in the Theory of Long Rod Penetration

. Journal of the Mechanics & Physics of Solids, 17: 141-150.

DOI      URL      [本文引用: 3]      摘要

T he theory of long rod penetration as given in a previous paper by the author is extended to take account of the deformation of a soft rod against a rigid target and the penetration of a rigid projectile into a soft target. It is shown that it is theoretically possible to have a decrease in depth of penetration with increasing impact velocity, and a method for deducing the average radius of the hole is given. The theory is compared with experimental results.
[216] Tate A.1979.

A simple estimate of the minimum target obliquity required for the ricochet of a high speed long rod projectile. Journal of Physics. D

. Applied Physics, 12: 1825-1829.

DOI      URL      [本文引用: 4]      摘要

Abstract A simple model for the minimum obliquity required to induce ricochet of a high speed long rod projectile from a thick target plate is suggested.
[217] Tate A.1986.

Long rod penetration models & mdash: Part II. Extensions to the hydrodynamic theory of penetration

. International Journal of Mechanical Sciences, 28: 599-612.

DOI      URL      [本文引用: 7]      摘要

The modified hydrodynamic theory of penetration is extended to take account of the transient, plastic-wave dominated and after-flow phases of penetration. It is also indicated how a more detailed flow field model of the primary phase of penetration leads to the modified Bernoulli equation and a relationship between the dynamic yield strength and the strength factors R t and Y p. The effect of the decelerative motion on the modified Bernoulli equation is also briefly examined. Finally, the theory is compared with experimental results of previous papers.
[218] Tate A, Green K E B, Chamberlain P G, Baker R G.1978.

Model scale experiments on long rod penetrators//Proceedings of 4th International Symposium on Ballistics, Monterey

.

[本文引用: 2]     

[219] Tu Z, Lu Y.2010.

Modifications of RHT material model for improved numerical simulation of dynamic response of concrete

. International Journal of Impact Engineering, 37: 1072-1082.

DOI      URL      [本文引用: 1]      摘要

Sophisticated numerical models are increasingly used to analyze complex physical processes such as concrete structures subjected to high-impulsive loads. Among other influencing factors for a realistic and reliable analysis, it is essential that the material models are capable of describing the material behaviour at the pertinent scale level in a realistic manner. One of the widely used concrete material models in impact and penetration analysis, the RHT model, covers essentially all macro features of concrete-like materials under high strain rate loading. However, the model was found to exhibit undesirable performance under certain loading conditions and some of the modeling issues have been discussed within a recent review paper by the authors. The present paper provides a more in-depth evaluation of the RHT model and proposes modifications to the model formulation to enhance the performance of the model as implemented in the hydrocode AUTODYN. The modifications include Lode-angle dependency of the residual strength surface, tensile softening law and the dynamic tensile strength function. The improvement of the performance of the modified RHT model is demonstrated using numerical sample tests, and further verified via simulations of two series of physical experiments of concrete penetration/perforation by steel projectiles. The results demonstrate an overall improvement of the simulation with the modified RHT model. In particular, the depth of penetration, projectile exit velocity and the crater size are predicted more favourably as compared to the test data. It is also shown that the modeling of the concrete tensile behaviour can affect sensibly the predicted perforation response (e.g., the projectile exit velocity), as is generally expected when the impact velocity exceeds the ballistic limit.
[220] Walker D, Anderson Jr C E.1991.

The Wilkins' computational ceramic model for CTH. SwRI Report,

4391 (002).

[本文引用: 1]     

[221] Walker J D.1999.

A model for penetration by very low aspect ratio projectiles

. International Journal of Impact Engineering, 23: 957-966.

DOI      URL      [本文引用: 3]      摘要

As the aspect ratio (L/D) of a projectile decreases and the projectile becomes more disk like, the penetration mode changes. A model for the penetration of low L/D projectiles has been developed to explain and predict the low L/D penetration event. The model divides the penetration into two phases: first a flyer plate type impact, and second, a crater growth phase. Calculations provided insight into the physical mechanism involved. Shortly after impact, the projectile enters a long period of constant velocity penetration. This behavior leads to the depth of penetration scaling with projectile diameter. A large crater grows in the target, and the projectile travels into a debris filled crater as a free body. The velocity is frozen in when release waves arrive from the free surface. In the model, the crater in the target is analyzed by assuming plastic constitutive response, with the motion caused by an impulsive load due to the impact. The final depth of penetration is obtained by combining a one-dimensional depth of penetration and a plastic target cratering response. The model compares well with both large scale numerical simulations and experimental data.
[222] Walker J D.1999.

An analytical velocity field for back surface bulging//Proceedings of the 18th international symposium on ballistics

, Lancaster: Technomic Publishing Co.:1239-1246.

[223] Walker J D.2001.

Ballistic limit of fabrics with resin//Proceedings of the 19th International Symposium on Ballistics

, Interlaken, Switzerland: 7-11.

[本文引用: 3]     

[224] Walker J D, Anderson Jr. C E, Goodlin D L.2001.

Tunsten into steel penetration including velocity, $L/D$, and impact inclination effects//Proceedings of the 19th international symposium on ballistics

,Interlaken Switzerland: 1133-1139.

[225] Walker J D, Anderson Jr. C E.1994.

The influence of initial nose shape in eroding penetration

. International Journal of Impact Engineering, 15: 139-148.

DOI      URL      摘要

The effect of projectile nose shape on penetration is examined numerically using the nonlinear, large deformation wavecode CTH. In particular, the impact of a tungsten alloy, long rod projectile into a 4340 steel target is investigated for three different nose shapes: blunt, hemispherical, and conical. The pressures are sufficiently high that erosion of the projectile begins immediately upon impact. The decays of the shocks are examined, as are the resulting material flow fields. Later-time effects are also explored, such as how the nose shape affects penetration, and how long each case takes to arrive at a quasi-steady-state flow configuration in which the tungsten-steel interface is completely determined by eroding plastic flow.
[226] Walker J D, Anderson Jr. C E.1995.

A time-dependent model for long-rod penetration

. International Journal of Impact Engineering, 16: 19-48.

DOI      URL      [本文引用: 4]      摘要

The one-dimensional, quasi-steady-state, modified Bernoulli theory of Tate [ J. Mech. Phys. Solids , 15 , 287 (1967)] is often used to examine long-rod penetration into semi-infinite targets. In general., the time histories of penetration predicted by the Tate model can be in good agreement with those computed from numerical simulations. However, discrepancies exist between the model and numerical simulations at the beginning and at the end of penetration. From insights provided by numerical simulations, assumptions are made concerning the velocity and stress profiles in the projectile and the target. Using these assumptions, the time-dependent, cylindrically-symmetric, axial momentum equation is explicitly integrated along the centerline of the projectile and target to provide the equation of motion. The model requires the initial interface velocity hich can be found, for example, from the shock jump conditions-and material properties of the projectile and target to compute the time history of penetration. Agreement between the predictions of this one-dimensional, time-dependent penetration model are in good agreement with experimental results and numerical simulations.
[227] Walters W, Williams C, Normandia M.2006.

An explicit solution of the Alekseevski--Tate penetration equations

. International Journal of Impact Engineering, 33: 837-846.

DOI      URL      [本文引用: 3]      摘要

The Alekseevski–Tate equations are typically used to predict the penetration, penetration velocity, rod velocity, and rod length of long rod penetrators and similar projectiles impacting targets. These nonlinear equations were originally solved numerically and more recently by the exact analytical solution of Walters and Segletes. However, due to the nonlinear nature of the equations, the penetration was obtained implicitly as a function of time, so that an explicit functional dependence of the penetration on material properties was not obtained. The current paper obtains the velocities, length, and penetration as an explicit function of time by employing a perturbation solution of the nondimensional Alekseevski–Tate equations. Simple (algebraic) analytical equations are given. Perturbation solutions of the Alekseevski–Tate equations were first undertaken by Forrestal et al., up to the first–order, and good agreement with the exact solutions was shown for relatively short times. In retrospect, this solution was only valid for penetrators impacting weak targets. The current study obtains a third-order perturbation solution and includes both penetrator and target strength terms, and is applicable for strong targets. The paper compares the exact solution to the perturbation solutions, and a typical comparison between the exact and approximate solutions for a tungsten rod impacting a semi-infinite steel armor target is shown. Also, alternate ways are investigated to normalize the governing equations in order to obtain an optimum perturbation parameter. In most cases, the third-order perturbation solution shows good agreement with the exact solution of the Alekseevski–Tate equations. In addition, simple equations based on the first–order perturbation solution are presented, which are accurate for the perforation of finite thickness (short penetration time) targets.
[228] Walters W P, Segletes S B.1991.

An exact solution of the long rod penetration equations

. International Journal of Impact Engineering, 11: 225-231.

DOI      URL      [本文引用: 1]      摘要

An exact solution is presented for the long rod penetration equations first formulated by Alekseevski in 1966 and independently by Tate in 1967. This analytical solution allows a faster and easier solution of the penetration equations, since stability considerations associated with any numerically integrated solutions are avoided. Additionally, an analytical solution provides greater insight into the penetration mechanism than a comparable numerically integrated solution.
[229] Wang X M, Zhao G Z, Shen P H, Zha H Z.1995.

High velocity impact of segmented rods with an aluminum carrier tube

. International Journal of Impact Engineering, 17: 915-923.

DOI      URL      [本文引用: 2]      摘要

Abstract In this paper, we apply the method of ballistic test to investigate the history and mechanism of the tungsten alloy segmented rod with aluminium carrier tube and corresponding continuous rod penetrating into semi-infinite steel target at velocities from 1.8 to 2.0 km / s. The length to diameter ratio of the segmented rod is 1 (LD = 1), the ratios of length of spacing between segments to diameter (s/d) are 0.5, 1.0 and 2.0 respectively. The results show that the power of penetration of the segmented rod with carrier tube is obviously higher then that of the corresponding continuous rod with carrier tube. Raising of the impact velocity, suitably increasing of the length of spacing between segments and filling the spacing with non-metallic material, etc. all can increase the penetrating power of the segmented rod. When impact velocity is 2.0 km / s, s / d=2.0, the penetrating power of the segmented rod is 10% higher than that of the corresponding continuous rod, if the spacing is filled with glass steel (non-metallic material), the power will be 20% higher. In this paper, we present a simplified model of based on hydrodynamics and penetrating mechanics. This model can properly describe the whole penetrating process of segmented rod penetrating into semi-infinite target. The shape of the crater and depth of penetration, etc. calculated are in good agreement with the results obtained by experiments.
[230] Weerheijm J, Van Doormaal J C A M.2007.

Tensile failure of concrete at high loading rates: New test data on strength and fracture energy from instrumented spalling tests

. International Journal of Impact Engineering, 34: 609-626.

DOI      URL      [本文引用: 1]      摘要

For the numerical prediction of the response of concrete structures under extreme dynamic loading, like debris impact and explosions, reliable material data and material models are essential. TNO-PML and the Delft University of Technology collaborate in the field of impact dynamics and concrete modelling. Recently, TNO-PML developed an alternative Split Hopkinson Bar test methodology which is based on the old principle of spalling, but equipped with up-to-date diagnostic tools and to be combined with advanced numerical simulations. Data on dynamic tensile strength and, most important, on fracture energy at loading rates up to 1000 GPa/s are obtained. The paper describes the test and measurement set-up, presents the new test data and the analysis of the test results. In addition, a rate-dependent softening curve is given which is based on the integrated findings so far.
[231] Wen H M, He Y, Lan B.2010.

Analytical model for cratering of semi-infinite metallic targets by long rod penetrators

. Science China (Technological Sciences), 53: 3189-3196.

DOI      URL      [本文引用: 4]      摘要

Analytical model is presented herein to predict the diameter of crater in semi-infinite metallic targets struck by a long rod penetrator. Based on the observation that two mechanisms such as mushrooming and cavitation are involved in cavity expansion by a long rod penetrator, the model is constructed by using the laws of conservation of mass, momentum, energy, together with the u-v relationship of the newly suggested 1D theory of long rod penetration (see Lan and Wen, Sci China Tech Sci, 2010, 53(5): 1364 1373). It is demonstrated that the model predictions are in good agreement with available experimental data and numerical simulations obtained for the combinations of penetrator and target made of different materials.
[232] Wen H M, He Y, Lan B.2011.

A combined numerical and theoretical study on the penetration of a jacketed rod into semi-infinite targets

. International Journal of Impact Engineering, 38: 1001-1010.

DOI      URL      [本文引用: 1]      摘要

A combined numerical and theoretical study is conducted herein on the penetration of semi-infinite targets by jacketed rods with different r j 0/ r c 0 ratios where r j 0 and r c 0 are the radii of the jacket and the core, respectively. The numerical results show that for smaller r j 0/ r c 0 ratios the u– v relationship changes only a little compared to that of unitary long rod penetrator of the same core material, hence, the u– v relationship of unitary (homogeneous) long rod penetration is also applicable for jacketed rod penetration. Model for cratering in semi-infinite targets by jacketed rods is then suggested by using the laws of conversation of mass, momentum and energy, together with the u– v relationship of unitary (homogeneous) long rod penetration and an analytical model for predicting the depth of penetration has also been given for jacketed long rods penetrating semi-infinite targets in co-erosion mode. A new criterion for transition from bi-erosion to co-erosion is proposed. It transpires that the present model is in good agreement with the experimental observations for EN24 steel jacketed tungsten alloy long rods penetrating semi-infinite armor steel targets in terms of crater diameter and penetration depth.
[233] Wen H M, Lan B.2010.

Analytical models for the penetration of semi-infinite targets by rigid, deformable and erosive long rods

. Acta Mechanica Sinica, 26: 573-583.

DOI      URL      [本文引用: 1]     

[234] Westerling L, Lundberg P, Holmberg L, Lundberg B.1997.

High velocity penetration of homogeneous, segmented and telescopic projectiles into alumina targets

. International Journal of Impact Engineering, 20: 817-827.

DOI      URL      [本文引用: 1]      摘要

Segmented and telescopic projectiles are designed to make efficient use of the higher impact velocities achievable with new acceleration techniques. This concept has been found to work against steel armour. In this study, we compare the penetration capability into an alumina target for these unconventional projectiles with that of a homogeneous projectile. The influence of segment separation distance and core-to-tube diameter ratio were simulated for the impact velocities 2.5, 3.0 and 3.5 km/s. The simulated final penetrations are compared to test results for one type of each of the homogeneous, segmented and telescopic projectiles at 2.5 and 3.0 km/s. Both simulations and tests show that the unconventional projectiles have better penetration capability than a homogeneous projectile with the same initial geometry.
[235] Westerling L, Lundberg P, Lundberg B.2001.

Tungsten long-rod penetration into confined cylinders of boron carbide at and above ordnance velocities

. International Journal of Impact Engineering, 25: 703-714.

DOI      URL      [本文引用: 7]      摘要

The purpose was to investigate the influence of impact velocity and confinement on the resistance of boron carbide targets to the penetration of tungsten long-rod projectiles. Experimental tests with impact velocities from 1400 to 2600 m/s were performed using a two-stage light-gas gun and a reverse impact technique. The targets consisted of boron carbide cylinders confined by steel tubes of various thicknesses. Simulations were carried out using the AUTODYN-2D code and Johnson olmquist's constitutive model with and without damage evolution. The experimental results show that the penetration process had different character in three different regions. At low-impact velocities, no significant penetration occurred. At high-impact velocities, the relation between penetration velocity and impact velocity was approximately linear, and the penetration was steady and symmetrical. In between, there was a narrow transition region of impact velocities with intermittent and strongly variable penetration velocity. In the lower part of this region, extended lateral flow of the projectile took place on the surface of the target. The influence of confinement on penetration velocity was found to be small, especially at high-impact velocities. The simulated results for penetration velocity versus impact velocity agreed fairly well with the experimental results provided damage evolution was suspended below the transition region.
[236] Yaziv D, Rosenberg G, Patrtom Y.

Differential ballistic efficiency of applique armour

. Shriveham, UK: 1986.

URL      [本文引用: 1]     

[237] Yaziv D, Walker J D, Riegel J P.1992.

Analytical model of yawed penetration in the 0 to 90 degrees range//Proceedings of the 13th international symposium on ballistics

, Stockholm: 1-3.

[本文引用: 3]     

[238] Zaera R, Sánchez-Gálvez V.1998.

Analytical modelling of normal and oblique ballistic impact on ceramic/metal lightweight armours

. International Journal of Impact Engineering, 21: 133-148.

DOI      URL      [本文引用: 1]      摘要

This paper presents a new analytical model developed to simulate ballistic impact of projectiles on ceramic/metal add-on armours. The model is based on Tate and Alekseevskii’s equation for the projectile penetration into the ceramic tile, whilst the response of the metallic backing is modelled following the ideas of Woodward’s and den Reijer’s models. The result is a fully new analytical model that has been checked with data of residual mass and residual velocity of real fire tests of medium caliber projectiles on ceramic/metal add-on armours. Agreement observed between experimental and analytical results confirmed the validity of the model. Therefore, the model developed can be a useful tool for optimisation of ceramic/metal armour design.
[239] Zhang L S, Huang F L.2004.

Model for long-rod penetration into semi-infinite targets

. Journal of Beijing Institute of Technology, 13: 285-289.

DOI      URL      [本文引用: 3]      摘要

Based on the equation of momentum conservation, an improved equation for the quisi-steady penetration of a long rod into homogeneous semi-infinite targets has been derived, assuming that the flow interface between the rod material and the target material is hemispherical and that the normal pressure on the interface is defined by the dynamic spherical cavity expansion. The equation has a form similar to the Tate equation, and the parameters in this equation have definite physical senses and practical values.
[240] Zhang X, Serjouei A, Sridhar I.2017.

Criterion for interface defeat to penetration transition of long rod projectile impact on ceramic armor

. Thin-Walled Structures.

[本文引用: 1]     

[241] Zhang X F, Li Y C.2010.

On the comparison of the ballistic performance of 10% zirconia toughened alumina and 95% alumina ceramic target

. Materials & Design, 31: 1945-1952.

[本文引用: 1]     

[242] Zhang X F, Li Y C, Zhang N S.2011.

Numerical study on anti-penetration process of alumina ceramic (AD95) to tungsten long rod projectiles

. International Journal of Modern Physics B, 25: 2091-2103.

DOI      URL      [本文引用: 3]      摘要

Numerical studies were conducted on the ballistic performance of alumina ceramic (AD95) tiles based on depth of penetration method, when subjected to normal impact of tungsten long rod projectiles at velocities ranging from 1100 to 2000 ms-1. The residual depth on after-effect target was derived in each case, and the ballistic efficiency factor was determined using the corresponding penetration depth on medium carbon steel. Anti-penetration experiment study of the AD95 ceramic tiles to tungsten long rod projectiles has been carried out to verify the accuracy of numerical simulation model. The result shows that numerical simulation results agree well with the corresponding experiment results and AD95 ceramic has excellent ballistic performance than medium carbon steel. The ballistic efficiency factor increases with velocity increasing when impact velocity lower than 1300 ms-1, and when it was higher than 1300 ms-1 the ballistic efficiency factor has almost no difference.
[243] Zhao J, Chen X W, Jin F N, Xu Y.2010.

Depth of penetration of high-speed penetrator with including the effect of mass abrasion

. International Journal of Impact Engineering, 37: 971-979.

DOI      URL      [本文引用: 1]      摘要

Mass abrasion is observed on the nose of projectile when a projectile strikes concrete target at high velocity. To evaluate the influence of the mass abrasion on the depth of penetration (DOP) limit, the relationship between the nose factor of the residual projectile after abrasion and the initial impact velocity is suggested according to the experimental data. Based on the dynamic cavity expansion theory, with considering the effects of varying nose factor and mass of projectile, a modified model is proposed to calculate the depth of penetration of kinetic energy penetrator. The model predicts that a theoretical maximum DOP exists due to the mass abrasion of the projectile. The model is checked by the different experimental data.
[244] Zhou H, Wen H M.2003.

Penetration of bilinear strain-hardening targets subjected to impact by ogival-nosed projectiles

. Theory and Practice of Energetic Materials, 5: 933-942.

URL      [本文引用: 1]      摘要

A theoretical study is presented herein on the penetration of ductile metal targets subjected to impact by ogival-nosed projectiles. The targets are made of bilinear strain-hardening materials with incompressibility. The paper consists of two parts. The first part is dynamic spherical cavity expansion model; the second is the penetration equations derived using the model. Closed-form solutions are obtained both for forces acting on the projectile nose and the depth of penetration. It is shown that the theoretical predictions are in good agreement with the available penetration data for aluminum targets subjected to impact by ogival-nosed as well as spherical-nosed projectiles.

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