Fatigue limit in borosilicate glass by interrupted static fatigue test

The threshold stress intensity factor, K-th, far sub-critical crack growth of borosilicate glass was measured in water environment using the interrupt ed static fatigue test. Bending tests with durations ranging from 1 h to 50 days were performed Around 15 specimens were tested at each condition and the constant stress applied varied from 70 to 95 MPa. The str ess intensity factor; K-w, applied to the weakest surviving sample during the stress hol d was calculated as a function of the dwell time. K-w was seen to decrease with the hold time until an invariant stress intensity factor corresponding to the fatigue limit (K-th approximate to 0.26-0.29 MPa root m) was reache d for durations larger than 10 days.