The onset of void coalescence during dynamic fracture of ductile metals
  Molecular dynamics simulations in three-dimensional copper have been performed to quantify the void coalescence process leading to fracture. The correlated growth of the voids during their linking is investigated both in terms of the onset of coalescence and the ensuing dynamical interactions through the rate of reduction of the distance between the voids and the directional growth of the voids. The critical inter-void ligament distance marking the onset of coalescence is shown to be approximately one void radius in both measures. 
E. T. Sepp\"al\"a, J. Belak, R. E. Rudd