NiTi合金强冲击荷载下微孔洞演化行为的分子动力学研究  

Molecular Dynamic Studies of Micro-voids Evolution Behavior Under Ultra Impact Loading for NiTi alloy

作　　者：崔晔晖 赵昂 曾祥国[1] CUI Yehui;ZHAO Ang;ZENG Xiangguo(College of Architecture and Environment,Ministry of Education Key Laboratory of Deep Earth Science and Engineering,Sichuan University,Chengdu 610065,China;School of Aerospace Engineering and Applied Mechanics,Tongji University,Shanghai 200092,China)

机构地区：[1]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,成都610065 [2]同济大学航空航天与力学学院,上海200092

出　　处：《材料导报》2024年第15期224-234,共11页Materials Reports

基　　金：国家自然科学基金委员会-中国工程物理研究院联合基金(U1430119,U1530140)。

摘　　要：本工作采用分子动力学模型研究了多晶NiTi合金在强冲击载荷作用下微孔洞的演化行为。为定量确定材料内部的孔洞体积分数,在后处理中采用PYTHON代码编程来统计孔洞体积。分子动力学的模拟结果很好地揭示了NiTi合金在不同冲击速度、冲击持时和晶粒尺寸下的孔洞演化机制和微观损伤机理。结果表明冲击速度的增大会导致冲击熔化效应,从而显著增加孔洞体积分数,并促使损伤行为从经典层裂向微层裂转变。在经典层裂中,冲击持时的增加不会影响孔洞的演化速率,但会延迟初始损伤时刻并使孔洞分布更靠近加载边界。而在微层裂行为下,缩短冲击持时将使损伤行为从微层裂退化为经典层裂,并降低孔洞的体积分数。此外,在数值模型中还研究了晶粒尺寸对孔洞演化的影响。在经典层裂情况下,由于晶粒间相互作用对孔洞生长的抑制作用,随着晶粒尺寸的减小,孔洞体积的增长速率会受到抑制。然而,当冲击速度增大到3 km/s时,冲击熔化行为会弱化晶粒尺寸的强化效果。在本工作中,分子动力学模拟对NiTi合金在不同参数下的损伤演化过程进行了很好的微观表征并揭示了相应的微观机理,其相应的数值结果可以为NiTi合金抗冲击结构设计提供理论参考,并为NiTi合金的制备优化提供了数值依据。In this work,the molecular dynamic model of nanocrystalline NiTi was applied to explore the micro-voids evolution process under intensive impact loading.To determine the voids volume fraction inside the materials,a PYTHON code was conducted to measure voids volume during the post-process for simulation results.The voids evolution process and the micro damage mechanism of NiTi alloy were well revealed by the molecular dynamic simulation under the different parameters including impact velocity,duration time,and grain sizes.It was found that the increasing of impact velocity would promote the growth of the voids volume significantly and the transformation of damage behavior from classical spallation to micro spallation.Under the classical spallation behavior,the increasing of the impact duration time would not affect the growth rate of voids.However,it will delay the damage initial time and make the voids distribution closer to the loading boundary.Meanwhile,the simulation results also proved that the reduction of the impact duration time would make the damage behavior degenerate from the micro spallation to classical spal-lation and decrease the volume fraction of voids.Finally,the grain size effect on voids evolution was also considered in the numerical model.Under the classical spallation situation,it was discovered that the voids increasing rate would be hindered with the reduction of the grain size due to the inhibiting effect of voids growth provided by grains interaction.However,when the impact velocity increased to 3 km/s,the grain size strengthening effect would be weakened by the impact melting behavior.In this work,molecular dynamics simulation gave the microscopic description of the NiTi damage evolution process under different parameters and revealed the corresponding microscopic mechanism.The numerical results could be used for the preparation optimization of NiTi alloy and provide theoretical reference for the design of NiTi structure.

关 键 词：NITI合金 孔洞演化 分子动力学 冲击荷载 

分 类 号：O385[理学—流体力学]