Fracture mechanical analysis of self-fatigue in surface compression strengthened glass plates

This paper presents a fracture mechanical analysis of the static fatigue and spontaneous fragmentation of surface compression-strengthened glass plates in the absence of applied load. It is suggested that if an initial surface crack which is sufficiently deep to penetrate into the tensile zone within the plate interior is introduced into the plate, then static fatigue, and eventually spontaneous fracture may follow. The crack problem for glass plates under various internal stress fields is solved and the stress intensity factor is obtained as a function of the crack depth. Using the fracture toughness and the slow crack growth characterization of the material, the conditions for no crack propagation, crack propagation leading to crack arrest, and that leading to catastrophic failure are established and discussed. The general results obtained are illustrated by means of a numerical example based on a 2 mm thick surface compression-strengthened glass plate exposed to water at 25° C.Such a problem was encountered in relation to an eye-lens during a consulting case by one of the authors (DPHH).