In-situ monitoring of catastrophic fracture behavior in MgO stabilized ZrO₂ by using M-L paint

The recently devlopoped ML(Mechano-Luminescence) technique enables macro-scale visualization of crack propagation during catastrophic failure, together with transformation zone (crack wake) in both crack front and side areas of Mg-PSZ in realistic time frame. The ML made it possible to precisely detect a relatively fast crack propagating in the speed range from 5 to 15 m/sec, thereby realizing so-called quasi-dynamic R-curve. A systematic observation of growth in wake height as well as wake length, was made successfully in quasi-dynamic condition. Effective-toughening applied-stress intensity factor increased up to 22 MPa√m. The h_o values obtained from the ML observation deviated significantly from that predicted by Evans-McMeeking model(J. Am. Ceram. Soc. 65, 242 (1982)); rahter it supports Marshall et al.'s results by interference microscopy and Raman spectroscopy (J. Am. Ceram. Soc. 73, 2659 (1990)) in the quasi-static crack propagation. It was also mentioned that conventional R-curves spanning over several millimeters range reported for long-crack systems such as DCB(Double Cantilever Beam), CT(Compact Tension), SENB(Single Edged Notched Bar), and etc. can not be explained by Evans-McMeeking model.