551 応力誘起変態によるPSZの靭性増加のマイクロメカニックス解析(OS7-7 微視的挙動・効果II)(OS7 微視構造を有する材料の力学)  [in Japanese] 551 Micromechanical Analysis of Stress-Induced Transformation-Toughening in Partially Stabilized Zirconia  [in Japanese]

In a partially stabilized zirconia (PSZ) containing tetragonal Z_rO_2 particles, a crack may be closed due to dilatational transformation strain of the particles induced in both a process zone and its wake surrounding the crack by enhanced stress at the vicinity of the tip of crack. In this study, micromechanical analysis on the toughness of such a PSZ is performed by modeling a crack surrounded by a process zone and its wake as a mixed double inclusion of the first kind which is an ellipsoidal inhomogeneous inclusion surrounded by an annular inclusion. Stress Intensity Factor of the crack in the PSZ, K^I_T, is derived and then its decrease ΔK due to stress-induced transformation of particles is formulated as a function of the transformation strain, the thickness of zone wake, and the volume fraction of particles. Numerical results of ΔK is good agreement with the experimental ones obtained by Swain et.al.