Quasi-dynamic visualization of crack propagation and wake evolution in Y-TZP ceramic by mechano-luminescence

The propagation of a macro-scale crack was visualized in yittria-tettragonal zirconia polycrystal (Y-TZP) ceramics using a mechano-luminescence (ML) of SrAl₂O₄:Eu,Dy. The transformation zone around the crack was also clearly detected in both the crack front and side areas of the Y-TZP in a realistic time frame. The ML made it possible to precisely detect a relatively fast crack propagating in the speed range from 20 m/s to 140 m/s, thereby realizing so-called quasi-dynamic R-curve. Effective toughening then commenced and the applied stress intensity factor increased to 20 MPa √m. The h_o values obtained from the ML observation deviated slightly from those predicted by the Evans-McMeeking model, and support Marshall's simple power law model of quasi-static crack propagation.