Crack Growth Threshold in Soda Lime Silicate Glass: Role of Hold-Time
J -. Guin, Sheldon M. Wiederhorn
Atomic force microscopy was used to examine the shapes of cracks and residual features left behind on the fracture surface after holding cracks at a stress intensity factor below the fatigue threshold for soda lime silicate glass. After propagating a crack at a stress intensity factor of K1 = 0.37 MPa m, the crack was held either at K1 = 0.24 MPa m or K1 = 0.1 MPa m. Cracks held at the higher K1 left featureless lines on the fracture surface. These lines became more pronounced as the hold-time increased and a corrosive notch was left behind the propagating crack. At about 30 nm from the crack tip, the crack surface displacement decreased to zero at the crack tip. The crack tip shape was that of an ogee arch. At the lower hold valued of K1, crack bifurcation occurred during which the crack became wavy, part of the crack propagating into the crack plane, part out of the crack plane when the crack was repropagated. A smaller crack tip displacement was observed for these cracks. Results of this study are believed to be a consequence of corrosion of the fracture surface caused by a basic solution formed when alkali ions (Na+ and K+) at the crack tip exchange with hydrogen ions in solution.
Journal of Non-Crystalline Solids
atomic force, crack growth threshold, crack tip blunting, fatigue threshold, microscopy, soda lime silicate