Yasuo Kogo1, Yutaka Kagawa2 and Hiroshi Hatta3
1Materials & Electronic Device Laboratory, Mitsubishi Electric Co., Sagamihara. Present address: Institute of Space and Astronautical Science, Sagamihara.
The fracture toughness of CeO2 stabilized ZrO2 (CeO2-ZrO2) has been measured under mode I, mode II and their mixed-mode conditions. The conventional single-edge-notched bending (SENB) test was carried out to obtain the mode I fracture toughness. The anti-symmetric four-point bending (AS4PB) test, which is the modified SENB test, was adopted for the mixed-mode and mode II fracture toughness tests. The obtained stress intensity factors at unstable fracture were discussed with the phase transformation behavior of ZrO2 and the phase-transformation toughening mechanism.
The results showed the maximum principal stress criterion and the non-coplanar strain energy release rate criterion is applicable to the KI-KII fracture curve. Under the mode II loading condition, the KIIC/KIC value of CeO2-ZrO2 was 0.6, which was lower than those of non-transforming brittle materials. The low KIC/KIIC value is attributed to the shielding effect by the transformation which is effective only on the mode I stress intensity.
ceria-stabilized zirconia, mixed-mode loading, fracture toughness, failure criteria, martensitic transformation, transformation toughening
Please do not copy without permission.