Hertzian contact damage in a highly porous silicon nitride ceramic

Hertzian indentation tests were performed to evaluate the contact damage behavior of a highly porous Si3N4 ceramic. Using a bonded-interface technique, the Hertzian contact damage patterns were examined. As a result of intragranular microfracture under Hertzian contact, a distributed subsurface damage region is developed beneath the indenter. It was found that the damage region extends progressively with increasing contact load. In strength tests, failures were observed to originate from Hertzian indentation sites, giving rise to a gradual strength degradation.