单晶与纳米多晶锡层裂的分子动力学研究  

Molecular dynamics study on spallation in single-crystal and nanocrystalline tin

作　　者：杨鑫 赵晗 高学军[1] 陈臻林[1] 王放[3] 曾祥国[2] YANG Xin;ZHAO Han;GAO Xuejun;CHEN Zhenlin;WANG Fang;ZENG Xiangguo(College of Environment and Civil Engineering,Chengdu University of Technology,Chengdu 610059,Sichuan,China;Loboratory of Deep Underground Science and Engineering of Minitry of Education,College of Architecture and Environment,Sichuan University,Chengdu 610065,Sichuan,China;School of Materials and Energy,Southwest University,Chongqing 400715,China)

机构地区：[1]成都理工大学环境与土木工程学院,四川成都610059 [2]四川大学建筑与环境学院深地科学与工程教育部重点实验室,四川成都610065 [3]西南大学材料与能源学院,重庆400715

出　　处：《爆炸与冲击》2023年第2期27-44,共18页Explosion and Shock Waves

基　　金：国家自然科学基金(11972095,12202081);四川省自然科学基金(2022NSFSC0443);四川省科技厅项目(2021YJ0525);工程材料与结构冲击振动四川省重点实验室资助项目(20kfgk02)。

摘　　要：低熔点金属的层裂是目前延性金属动态断裂的基础科学问题之一。采用非平衡态分子动力学方法模拟了冲击压力在13.5~61.0 GPa下单晶和纳米多晶锡的经典层裂和微层裂过程。研究结果表明:在加载阶段,冲击速度不影响单晶模型中的波形演化规律,但影响纳米多晶模型中的波形演化规律,其中经典层裂中晶界滑移是影响应力波前沿宽度的重要因素;在单晶模型中,经典层裂和微层裂中孔洞成核位置位于高势能处;在纳米多晶模型中,经典层裂中的孔洞多在晶界(含三晶界交界处)处成核,并沿晶定向长大,产生沿晶断裂,而微层裂中孔洞在晶界和晶粒内部成核,导致沿晶断裂、晶内断裂和穿晶断裂;孔洞体积分数呈现指数增长,相同冲击速度下单晶和纳米多晶Sn孔洞体积分数变化规律一致;经典层裂中孔洞体积分数曲线的两个转折点分别表示孔洞成核与长大的过渡和材料从损伤到断裂的灾变性转变。One of the fundamental scientific problems of dynamic fracture of ductile metals is spallation of low melting point metals. The classical spallation and micro-spallation of single-crystal(SC) and nanocrystal(NC) tin were carried out using the non-equilibrium molecular dynamics(NEMD) at shock pressures of 13.5-61.0 GPa. In order to achieve the spallation in the SC and NC models, the piston-target method was utilized. Specifically, the rigid piston was assigned an initial velocity, then the piston impacted the target to generate stress wave, and the stress waveform was controlled by adjusting the loading time after the length of the model along the shock direction was determined. The simulation results show that: during the loading stage, the shock wave velocity has no influence on the waveform evolution of the SC Sn model, but it does have an effect on the waveform evolution of the NC Sn model, in which the front width of the stress wave in classical spallation of the NC Sn model is mainly affected by grain boundary sliding. The void nucleation sites in classical spallation and micro-spallation are found at high potential energies in the SC model. In the NC model, for the classic spallation, voids mostly nucleate at grain boundaries(including the triple junctions of the grain boundaries) and grow along grain boundaries, resulting in intergranular fractures;for the micro-spallation, voids nucleate at the grain boundary and inside the grain, resulting in intergranular fracture,intragranular fracture, and transgranular fracture. The void volume fraction increases exponentially, and the variation law of void volume fraction of SC and NC Sn is the same under the same impact velocity. The two turning points of the void volume fraction curve in classical spallation represent the transition from nucleation to growth and the catastrophic transition from damage to fracture.

关 键 词：非平衡态分子动力学 单晶与纳米多晶锡 应力波演化 断裂方式 孔洞体积分数 

分 类 号：O383[理学—流体力学] O347.4[理学—力学]