Application of Mechanoluminescence for the Dynamic Visualization of an Alumina Fracture

Abstract The propagation of cracks was quantitatively analyzed in Al2O3 ceramic using the mechanoluminescence (ML) of SrAl2O4:Eu,Dy. The bridging zones behind the crack tip were clearly detected in the crack path of Al2O3 within a realistic time frame. The magnitudes and shapes of the bridging stress distributions changed with the advancing cracks. They continued to change with the change in the applied load even after the cessation of crack propagation. Effective toughening then commenced, and the applied stress intensity factors dramatically increased up to ∼50 MPa√m . The expected KTip values based on the instantaneous bridging stress distributions obtained from the ML observations deviated greatly from those obtained from the measurement using the conventional crack tip lengths; rather, they support the results obtained when bridging tips were used in the quasidynamic crack propagations.