Molecular Insight into the Deformation of Single Crystal Copper Loaded by High-Speed Shock Wave

Changjiang Zhang,Yupeng Zhao,Bin Fang,Jiuling Meng,Jingrui Cao,Tao Lü

doi:10.3390/met11030446

Abstract

Molecular dynamics simulations were performed to study the evolution of single crystal copper with and without a nanovoid (located at the middle of crystal with a diameter of ~2.9 nm) when loaded with shock waves of different velocities. The simulation results show that the average particle velocity of single crystal copper linearly relates to the velocity of the loaded shock wave for both the systems (crystal with and without a nanovoid). When loaded by the shock wave, the equilibrated temperature and pressure of the system with a nanovoid are found to be slightly larger than those of the system without the nanovoid, while the volume of the system with the nanovoid is found to be lower than that of the void-free system. The single crystal copper undergoes a phase transition from face-centered cubic (FCC) to hexagonal-close packed (HCP) and a dislocation structure forms around the nanovoid. The existence of a nanovoid can induce the rearrangement and deformation of the crystalline structure and eventually lead to the plastic deformation of the system. This work provides molecular-level insight into the effect of nanovoids on the shock plasticity of metals, which can aid in the ultimate application of the control of material structure damage in shock-wave propagation.

Highlights

A material may undergo structural damage when a strong shock wave propagates through a material because real materials may contain a large number of defects, such as vacancies [1,2,3], dislocations [4,5,6,7,8,9], grain boundaries [10,11,12,13], and micropores [14]
Bringa et al [34] carried out nonequilibrium molecular dynamics method (NEMD) to simulate a nanometer single crystal copper loaded by a plane shock wave
Molecular dynamics (MD) simulations with the multi-scale shock technique (MSST) method are performed to study two different single crystal copper systems loaded by a compressive shock wave with different velocities

Summary

Introduction

A material may undergo structural damage when a strong shock wave propagates through a material because real materials may contain a large number of defects, such as vacancies [1,2,3], dislocations [4,5,6,7,8,9], grain boundaries [10,11,12,13], and micropores [14]. Bringa et al [34] carried out nonequilibrium molecular dynamics method (NEMD) to simulate a nanometer single crystal copper loaded by a plane shock wave. Neogi and Mitra [36] studied the shock response of a nanovoid closed/open-cell copper material using NEMD simulations and found that the Hugoniot elastic limit (HEL) point decreases with increasing porosity. There are a few studies on the shock wave loading of single crystal copper using the multi-scale shock technique (MSST) in MD simulations. These studies paid little attention to the effects of nanovoid on thermodynamic parameters. MD simulations with the MSST method are performed to study two different single crystal copper systems loaded by a compressive shock wave with different velocities.

Simulation Methodology

Phase Transition and Dislocation Pathway

Time Evolution of System Stress

Conclusions