Mechanism of ring crack initiation in Hertz indentation of monocrystalline silicon analyzed by controlled molecular dynamics

The mechanism of ring crack initiation in the Hertz indentation of monocrystalline silicon with no preexisting defect has been analyzed by controlled molecular dynamics. It has been found that microvoids that develop into a ring crack can be generated outside the outer periphery of the contact area between the silicon and an indenter, such that the static stress and dynamic stress associated with acoustic waves locally transform the monocrystal structure to a polycrystal one, and then the static stress causes cross slips at grain boundaries to cause microvoids.