Cracking phenomena in lithium-di-silicate glass ceramics

Lithium-di-silicate glass ceramic (Li2O,SiO2) With uniformly oriented cryst als was placed on a Vickers indentation with extrusion axis horizontally pa rallel to the base axis, The material was rotated through 0 degrees -90 deg rees and at each angle a 20 N load was applied to ascertain the crack path. It was observed that the crack length decreases and the crack deviates Fro m its original path with increasing angle. The deviation of the crack was c orrelated with the component of the crack driving force and the theoretical strength of the aligned crystals at different angles.