Molecular dynamics simulations of ejecta size distributions for shock-loaded Cu with a wedged surface groove

Large-scale molecular dynamics (MD) simulations are performed to study the dynamic fragmentations of microjet from shock-loaded Cu with a wedged surface groove. The influences of shock intensity, vertex angle and depth of the groove on the fragmentation morphologies as well as the ejecta size distributions are explored. Two representative jet morphologies have been obtained, the microsheet and the microjet of lacrosse racket shape. The time evolution of ejecta volume distributions and the underlying fragmentation mechanisms are analyzed in detail. For the microsheet, the steady-state volume distribution takes the form of the sum of a power law with an exponent about 1.15 and an exponential or exponential-like form in the small and large size limits, respectively. For the microjet of lacrosse racket shape, a heterogeneous fragmentation appears, where the top part expands and fragments in three-dimensional (3D) space while the bottom part breaks up in two-dimensional (2D) space. Though the ejecta volume distributions in the top and bottom regions also contain a power law and an exponential or exponential-like form separately, the exponents in the power laws and the characteristic volume scales in the exponential distributions are different.