Methodology for Studying Brittle Fracture of HTHP Diamond Single Crystals by Crack Propagation Analysis under Shock Load

The behavior of type IIa HTHP single crystal diamonds under shock loads created by means of Hopkinson–Kolsky pressure bars is studied. Controlled variation of load pulse magnitude and duration makes it possible to trace the complete history of crack progression. It ranges from crack initiation in regions of peak stress, through rapid crack propagation and the formation of a smooth surface, to stable crack growth accompanied by the formation of a densely packed array of fine ridges, and eventually to a deceleration and discontinuous crack movement, which culminate in a stepped structure upon the completion of step formation. Atomic force microscopy is employed to reveal the topographic characteristics of the fracture surface with spanning dimensions from 3 to 600 nm. The three-dimensional distribution of equivalent von Mises stresses throughout the entire crystal and respective crystal fragments after brittle fracture is also simulated in the study.