Investigations of void collapse in nanoporous Cu by molecular dynamics simulations

Mechanical responses of nanoporous Cu samples under various loading conditions are investigated by molecular dynamics simulations. Effects of loading mode, initial void size, temperature, and void distribution are analyzed. The simulations show that the collapse time under uniaxial compression is about three times that under triaxial compression, and the collapse rate increases as the temperature rises. Dislocation nucleation is found to stimulate the collapse of void. For samples with a single void, the final dislocation density under triaxial compression is lower than that under uniaxial compression, which is due to that the dislocation accumulation rate greatly slows down after the void is fully collapsed. For samples with multiple voids, the dislocation accumulation rate under triaxial compression is much faster than that under uniaxial compression, resulting in higher dislocation density under triaxial compression. Irrespective of the initial void size, the evolutions of compression stress and void volume fraction remain invariant when the initial void volume fraction is fixed; however, the dislocation density decreases as the initial void radius increases.