Investigation of the Subcritical Crack Growth Process in Glass by Atomic Force Microscopy
Jean-Pierre Guin, Sheldon M. Wiederhorn
To investigate the possibility of cavity formation in silica glass during subcritical crack growth, the topography of fracture surfaces formed in water at a crack velocity of 8.10-11 m/s was mapped using an atomic force microscope. The objective of the study was to determine how well the two halves of a crack in silica glass matched by establishing a three dimensional quantitative comparison of the shape of the two surfaces. This procedure uses a minimization routine to correct first order and quadratic deformations between the two AFM images of the crack surfaces. A three-dimensional image representing topographical differences between the corresponding fracture surfaces followed a Gaussian law centered on zero with a standard deviation, s, of 0.22 nm. Within the resolution of the technique, 6 nm within the fracture surface and 0.3 nm normal to the fracture surface, no evidence for cavitation was found in silica glass. It is suggested that subcritical crack growth in silica glass occurs in a brittle way by the successive snapping of bonds as the crack advances.
atomic force microscopy, brittle fracture, glass, subcritical crack-growth fractography