日本金属学会誌

J. Japan Inst. Metals, Vol. 57, No. 1 (1993),
pp. 21-28

R-Curve Behavior of CeO2-Stabilized ZrO2 and Stress Intensity Factor at Crack-Tip Measured with Laser Caustics

Yasuo Kogo1, Yutaka Kagawa2 and Hiroshi Hatta1

1Institute of Space and Astronautical Science, Sagamihara
2Institute of Industrial Science, The University of Tokyo, Tokyo

Abstract:

The stress intensity factor calculated from far field stress and the shape of the specimen (K) and that at the crack-tip (Ktip) of CeO2 stabilized ZrO2 (CeO2--ZrO2) were measured using DCB (Double cantilever beam) test specimen. From observed K and Ktip, contribution of transformation toughening (Δ K) was examined based on the relation
\begin{equation*}
K=Ktip+Δ K.
\end{equation*}

Compression splitting test method, compressing the top of the DCB specimen, was applied to achieve the slow crack growth of CeO2--ZrO2. The laser caustic method was also applied to observe the stress intensity factor at the crack-tip of the specimen.

The results showed that the K was increased with increasing crack extension (R-curve behavior). Crack extension was started around K of 3 MPa√m, and the K was increased up to 7 MPa√m, where K was saturated. On the other hand, the Ktip showed constant value in the rage of 2~ 3 MPa√m during the crack extension. With these results, the shielding effect, which is the relaxation mechanism of stress intensity, was experimentally verified.


(Received June 24, 1992)

Keywords:

ceria-stabilized zirconia, martensitic transformation, transformation toughening, R-curve behavior, caustics


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