分子动力学模拟研究未冻水对冰晶体力学性质的影响  

Study on influence of unfrozen water on mechanical properties of ice crystals by molecular dynamics simulations

作　　者：陈文婷 张鹏 陈雪萍 马旭 张莲海 吴青柏 CHEN Wenting;ZHANG Peng;CHEN Xueping;MA Xu;ZHANG Lianhai;WU Qingbai(State Key Laboratory of Frozen Soil Engineering,Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences,Lanzhou 730000,China;University of Chinese Academy of Sciences,Beijing 100049,China;Joint NMR Laboratory for Freeze-Thaw Processes in Soils,Lanzhou 730000,China)

机构地区：[1]中国科学院西北生态环境资源研究院冻土工程国家重点实验室,甘肃兰州730000 [2]中国科学院大学,北京100049 [3]磁共振冻融成冰过程动态分析联合实验室,甘肃兰州730000

出　　处：《冰川冻土》2023年第2期624-640,共17页Journal of Glaciology and Geocryology

基　　金：甘肃省科技重大专项(22ZD6FA004);甘肃省中小企业创新基金项目(22CX3JA003);冻土工程国家重点实验室自主课题(SKLFSE-ZT-202103)资助。

摘　　要：冰力学性质的研究在冻土工程、冰工程中都占据极其重要的地位,冰中未冻水含量的变化会导致冰整体性质随之改变。目前,在微观分子尺度上针对冰中未冻水含量控制因素方面的研究尚不充分。本研究通过分子动力学方法模拟了5种温度、3种应变速率、4种晶粒尺寸、3种升温速率下单晶冰与多晶冰的单轴拉伸与压缩试验,研究了不同影响因素下冰晶体力学性质及内部的微观结构变化,揭示了分子尺度上未冻水在冰晶体变形过程中的产生过程与变化规律,以及未冻水比例对冰晶体力学性质影响的内在机理。模拟结果显示,单晶冰力学性质与未冻水比例间的关系不显著,与冰晶体六元环结构的破损程度直接相关。此外,力学性质受温度、应变量、应变速率等多因素影响,且在拉伸和压缩过程中单晶冰均表现出明显脆性破坏,其强度随温度降低和应变速率加快而增强。相比之下,多晶冰力学性质与未冻水比例变化密切相关,且未冻水比例主要受温度、晶粒大小及其界面状态控制。而且,多晶冰对温度和应变速率更敏感,说明晶界处的结构变化对其力学性能起重要作用。与弹性变形不同,晶界滑移、晶粒旋转、非晶化和再结晶等过程主导多晶冰的塑性变形。In permafrost and ice engineering,the study on mechanical properties of ice is of great importance,wherein changes in content of unfrozen water inside ice can lead to overall changes of properties of ice.At present,the study at microscopic molecular scale on control factors of unfrozen water content in ice presents non-adequate.As a relatively special solid material,ice can be classified into single-crystal and polycrystalline ones in terms of their morphological difference,the latter of which usually exists in a polycrystalline structural state,in nature and artificial laboratory environments.And the structural difference between polycrystals and single crystals is mainly that the former have grain boundaries,that is,some relatively disordered or less neat regions in the middle of two regularly arranged lattices.In contrast,the entire structure of a single crystal is a long-range ordered crystal structure.Namely,polycrystals can be viewed as being composed of many single crystal particles.The exploration on mechanical properties of polycrystalline ice basing single-crystal ice can help us to further understand its microstructural changes.In this study,after building single-crystal and polycrystalline ice models,setting up molecular force fields,and initializing the system for models,uniaxial tensile and compressive tests were implemented on single-crystal and polycrystalline ices by molecular dynamics simulations,under five temperatures,three strain rates,four grain sizes and three heating rates.The mechanical properties of ice crystals and internal microstructural changes inside them were then investigated,under different influencing factors,aiming to reveal the underlying influencing mechanism of unfrozen water proportion on mechanical properties of ice crystals.In terms of simulation results,for single-crystal ice,mechanical properties of them appear weak relation to unfrozen water proportion,but significant dependence on breakage degree of six-membered ring structures,as well as they are influenced by temper

关 键 词：分子动力学 冰晶体 未冻水 力学性质 控制作用 

分 类 号：P343.63[天文地球—水文科学]