Abstract
A crack induced by Vickers indentation were observed using scanning probe microscope. Although a crack propagated straight in soda lime glass, the region near the crack was found to be not smooth but slightly gibbous. This phenomenon probably means that plastic deformation occurred during fracture by local stress field at the crack tip in spite of its brittleness. A crack in Si3N4 ceramics discontinuously propagated in the grain and grain boundary. The discontinuous region after cracking was not level, namely the grain for crack bridging showed a little concavo-convex. It seems that the deformation of the grain resulted from bridging force. Furthermore, some grain boundaries at the crack tip became hollow, which is probably enbrio of the fracture.
