分子动力学方法在金属材料动态响应研究中的应用

邓小良; 李博; 汤观晴; 祝文军

doi:10.11858/gywlxb.20190750

分子动力学方法在金属材料动态响应研究中的应用

doi: 10.11858/gywlxb.20190750

邓小良^1,,
李博¹,
汤观晴^{1, 2},
祝文军¹

1.
中国工程物理研究院流体物理研究所冲击波物理与爆轰物理重点实验室，四川绵阳　621999
2.
湖南大学材料科学与工程学院，湖南长沙　410082

基金项目: 科学挑战专题（TZ201601）；冲击波物理与爆轰物理重点实验室基金（6142A0305010717, JCKYS2018212011）

详细信息

作者简介:
邓小良（1978－），男，博士，副研究员，主要从事材料动态力学性能研究. E-mail: xiaoliangdeng@163.com

中图分类号: O521.2; O347.5
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出版历程
- 收稿日期: 2019-03-27
- 修回日期: 2019-04-28

Application of Molecular Dynamics Simulation to Dynamic Response of Metals

1.
National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621999, China
2.
Department of Materials Science and Engineering, Hunan University, Changsha 410082, China

摘要

摘要: 随着计算机技术和实验诊断技术的发展，分子动力学（MD）方法在冲击动力学领域发挥着越来越重要的作用。从MD方法的基本原理出发，介绍了积分算法、相互作用势、常用的数据处理方法，系统梳理了MD方法在冲击加载下金属材料的塑性变形、相变、动态损伤断裂（层裂）等研究的应用。其中：在冲击塑性方面，主要阐述单晶、双晶和多晶体系中的塑性变形机理，以及变形过程与微结构等的联系；在冲击相变方面，主要以金属铁为例，介绍耦合冲击相变与冲击塑性的MD计算模拟工作；在动态损伤断裂方面，主要阐述冲击加载下金属材料中孔洞动态演化及贯通、激光加载下材料的动态响应等工作。最后，对MD方法的未来应用进行了展望，以期为相关领域的研究提供参考。
- 分子动力学 /
- 冲击塑形 /
- 冲击相变 /
- 动态断裂
Abstract: With the development of computer science and technology and diagnostic techniques, molecular dynamics (MD) simulation plays an increasingly important role in the field of shock dynamics. This review presents the basic principle of MD firstly, followed by integrated algorithm, inter-atom potentials, and some widely used data processing methods. Then the applications of MD in the plastic deformation of metals, phase transitions, and damage and fracture under shock loading (spallation) are presented in a systematic manner. The shock plasticity is focused on the micro-mechanisms of plastic deformation and the relationship between the deformation process and micro-structures in single crystals, twin crystals, and polycrystals. In terms of shock-induced phase transitions, the iron is taken as an example to emphasize the research focusing on the coupling of shock transitions and shock plasticity. The contents of dynamic damage and fracture mainly cover the void evolution and coalescence, dynamic response of materials under laser loading, and so on. Finally, a brief summary and perspective of MD regarding to future applications are offered, intending to provide the further information for the related researchers.
- molecular dynamics simulation /
- shock plasticity /
- shock phase transition /
- dynamic fracture

HTML全文

图 1 （a）冲击加载下样品中的波结构示意图，（b）实验测量的应力剖面或自由面速度历史剖面示意图

Figure 1. (a) Diagram of wave structure in the sample under impact loading; (b) diagram of the stress profile or the free surface velocity history profile measured in the experiment

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图 2 单晶Ta沿[110]冲击形成的变形孪晶图案^[20]：（a）原子相对于冲击方向的取向着色，（b）仅显示非bcc原子

Figure 2. Deformation twin pattern observed in Ta for impact loading along [110] direction: (a) atoms are colored according to the orientation relative to the impact direction; (b) snapshot for non-bcc atoms in the simulation

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图 3 含CTB（a）和SITB（b）的双晶铜在粒子速度u_p=0.375 km/s的冲击加载下的x-t图，以及不同加载强度下弹性波在SITB处引起的塑性变形（（c）～（e））（P表示所处区域为塑性变形区，9R表示重复的堆垛序列：ABCBCACAB）^[23]

Figure 3. (a) and (b) represent the x-t diagram of the twin-crystal copper containing CTB and SITB under the impact loading with u_p=0.375 km/s, (c)–(e) represents the plastic deformation caused by elastic wave at SITB under different loading strengths (The P indicates the plastic deformation region. The 9R represents the repeated stacking sequence: ABCBCACAB.)^[23]

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图 4 纳米柱状晶在冲击压缩下的缺陷结构图（a）及对应的取向分析图（b）^[25]

Figure 4. Defect structure diagram (a) and corresponding orientation analysis diagram (b) of nano-columnar crystals under impact compression

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图 5 不同速度下应力剖面和原子结构图（bcc结构原子未显示，红色、黄色和黑蓝色分别代表hcp相、fcc相和晶格缺陷；弹性波区、塑性波区、混合相区和Hugoniot状态区的分界处用字母a、b、c表示）^[8]

Figure 5. Stress profiles and atomic structure diagrams at different velocities (The bcc structure are not shown. Red represents hcp phase, yellow represents fcc phase, and black and blue represent lattice defects. The boundaries between the elastic wave region, the plastic wave region, the mixed phase region and the Hugoniot state region are given by the letters a, b, and c, respectively.)^[8]

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图 6 不同晶向加载下金属铜中单孔洞的演化及周围位错发射过程^[59]

Figure 6. Evolution of single void and surrounding dislocation emission process in copper for different grain orientations^[59]

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图 7 多晶钽层裂的微观结构分析（(c)、(d)、(e)对应(a)和(b)中标记的矩形区域；(c)是在层裂较远的区域，初期层裂表现为样品中出现分散的小孔洞，EBSD扫描显示了晶界和晶内的孔洞；(d)和(e)为层裂正下方区域，该区域内颗粒尺寸较小）

Figure 7. Microstructural analysis of polycrystalline tantalum spallation (The marked rectangular regions in (a, b) correspond to (c, d, e). (c) Away from the spallation, incipient spallation can be seen as voids scattered throughout the specimen. The EBSD scans show the voids at the grain boundaries as well as grain interiors. The particle size is small within regions of (d) and (e) which are around the spallation zone.)

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图 8 MD模拟与实验在自由面处测得的层裂强度与应变率的关系曲线^[75]

Figure 8. Relationship between the laminar fracture strength and the strain rate measured at the free surface of MD simulations and experiments^[75]

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图 9 Cr靶在30个脉冲激光照射下产生不同类型的纳米尖峰的SEM显微照片（激光能量密度为0.3 J/cm²，该能量密度小于导致相爆炸能量密度阈值的10%）

Figure 9. SEM micrograph of different types of nanospikes generated in Cr target irradiated by 30 laser pulses (The laser energy density was 0.3 J/cm², less than 10% of the energy density threshold for phase explosion.)

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图 10 双温模型模拟中能量密度为298 mJ/cm²（接近相爆炸阈值）、脉冲宽度为200 fs的激光辐照大块Cr靶时得到的原子构型图^[87]

Figure 10. Atomic configuration diagram was obtained by the laser irradiation of a large Cr target with the energy density of 298 mJ/cm² (close to the phase explosion threshold) and pulse width of 200 fs in the two-temperature model simulation

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