The atomic force microscope (AFM) was used to explore the nature of features formed on the surfaces of cracks in soda-lime-silicate glass that were held at stress intensity factors below the crack growth threshold. All studies were conducted in water. Cracks were first propagated at a stress intensity factor above the crack growth threshold and then arrested for 16h at a stress intensity factor below the threshold. The stress intensity factor was then raised to reinitiate crack growth. The cycle was repeated multiple times, varying the hold stress intensity factor, the hold time, and the propagation stress intensity factor. Examination of the fracture surface by optical microscopy showed surface features that market the points of crack arrest during the hold time. These features were identical to those reported earlier by Michalske in a similar study.
