Temperature sensitivity of void nucleation and growth parameters for single crystal copper: a molecular dynamics study

Abstract

The effect of temperature on the void nucleation and growth is studied using the molecular dynamics (MD) code LAMMPS (Large-Scale Atomic/Molecular Massively Parallel Simulator). Single crystal copper is triaxially expanded at 5 × 109 s−1 strain rate keeping the temperature constant. It is shown that the nucleation and growth of voids at these atomistic scales follows a macroscopic nucleation and growth (NAG) model. As the temperature increases there is a steady decrease in the nucleation and growth thresholds. As the melting point of copper is approached, a double-dip in the pressure–time profile is observed. Analysis of this double-dip shows that the first minimum corresponds to the disappearance of the long-range order due to the creation of stacking faults and the system no longer has a FCC structure. There is no nucleation of voids at this juncture. The second minimum corresponds to the nucleation and incipient growth of voids. We present the sensitivity of NAG parameters to temperature and the analysis of double-dip in the pressure–time profile for single crystal copper at 1250 K.

Fracture during high-velocity impact of copper plates: a molecular dynamics study

“…For the impact of copper plates at 1100 m/s impact velocity, the spall of the material takes place at 160 kbar pressure. This validates the void nucleation threshold (160 kbar) obtained under triaxial strain conditions [2]. The stochastic effect on spallation process has been studied by performing impact of copper plates at 1000 m/s impact velocity.…”

“…No significant void nucleation is observed in the neighbouring regions where tensile pressure stays below 160 kbar. This validates the void nucleation threshold (160 kbar) obtained for crystal copper under triaxial strain conditions [2]. As soon as spall of the material takes place, pressure in the region rapidly drops to zero.…”

“…Impact is done with an impact velocity of 1100 m/s. The typical strain-rate in this impact simulation is ∼O(10 9 /s), comparable with the triaxial strain simulation [2].…”

“…In the present work, we validate the void nucleation threshold (160 kbar) obtained under triaxial strain conditions [2] by studying the impact of copper plates at 1100 m/s. We also show the stochastic behaviour of spall process for the impact velocities close to the spall threshold of the material.…”

Identification of best fit parameters of void nucleation and growth model using particle swarm technique

“…The best fit parameters of the NAG model can be obtained by fitting to the results of the MD simulations. The best fit parameters for Copper (Cu) [4] have been obtained using this approach. Nb and Mo are the materials used for development of structural components of fusion and nuclear engineering devices.…”