Deformation mechanisms and stress triaxiality in spall failure in niobium: a molecular dynamics study

The underlying mechanisms associated with dynamical failure are not fully understood, this is particularly true regarding the plastic deformation around the nucleation and growth of porosity that eventually leads to failure. We used large-scale non-equilibrium molecular dynamics simulations to investigate the shock loading and subsequent failure of single crystal niobium samples. State-of-the-art analysis of the MD trajectories provides information about the three-dimensional stress states associated with void nucleation, growth, and coalescence as well as dislocation-based plasticity phase transformation and recrystallization with atomistic resolution. We will discuss how shock strength and defects affect the nucleation and growth of porosity, the associated mechanisms, and how they affect the resulting nanostructure post failure. The results can help with the interpretation of ongoing experiments.