Observation of stable crack growth in Al2O3 ceramics using a scanning acoustic microscope

We employed ultrasonic techniques in order to gain information on the R-curve behavior of Al2O3 ceramics. A reduction in the sound velocity has been observed at the crack tip of subcritically grown cracks. The measurements were carried out by time-of-flight measurements, and by evaluating the V(z) curves obtained from a scanning acoustic microscope. Furthermore, we could also observe effects related to the interaction of serrated crack walls by in situ experiments in the scanning acoustic microscope.