In-situ Observation of Fatigue Crack Propagation in Soda-Lime Glass with Vickers Indentation-Induced Initial Crack under Bending

Abstract

Small cracks propagate at the glass surface due to the combined effects of water vapor and applied load. This phenomenon is known as glass fatigue. In this study, four-point bending fatigue tests under static and cyclic loading conditions were conducted for the soda-lime glass plate specimens with the initial crack and indentation pit induced by Vickers diamond indentation. Fatigue cracks were observed by the in-situ crack observation system using optical microscopy in order to obtain the relationship between crack growth rate, da/dt, and maximum stress intensity factor, K_max, during fatigue tests. The da/dt decreased and then increased with the K_max value. In addition, photoelasticity was applied to measure the residual stress distribution generated on the surface of the glass. The results showed that the da/dt at the early stage varied with indentation load due to the residual stress, whereas the effect of the indentation load on the da/dt was not observed in the region without residual stress.