The spallation of single crystal SiC: The effects of shock pulse duration

Abstract

Shock-induced spall in initial defect-free single crystal SiC is investigated using molecular dynamics (MD) simulation. Three shock pulses ranging from triangle to square are adopted to study the effects of pulse duration on spallation. The evolution of micro-structure and damage are analyzed in detail. Shock-induced plasticity is found to include deformation twinning and structure changes from 4 to 5 fold coordination number. These deformations disappear upon unloading causing numerous defects. Morphology of spallation is found to depend on these damage strongly. Furthermore, the spall strength obtained from free surface velocity and bulk are compared. Triangle pulse yields a higher value in the spall strength calculated from free surface velocity, while square pulse enjoys a similar result in both methods. Moreover, the theoretical total spall thicknesses are derived basing on the theory of spallation. The prediction of the total spall thicknesses are made using the stress waveform right before reflection and the spall strength. A good agreement between the simulation and the prediction is found in triangle wave.