Experiments were conducted to initiate cracks on soda-lime-silica glas
s by repeated indentation at a single point with different subcritical
loads (0.1, 0.15, 0.25, 0.5 N) and a critical load of 1 N, similar to
metal fatigue. It was observed that the diagonal length of the impres
sion after each indentation cycle at different subcritical loads incre
ased to a limit until hair-line radial cracks were initiated leading t
o eventual cracking. This phenomenon was analyzed based on cumulative
residual stress and plastic deformation at the vicinity of the indenta
tion causing eventual cracking.