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 (ΔK) was examined based on the relation
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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\sqrtm, and the K∞ was increased up to 7 MPa\sqrtm, where K∞ was saturated. On the other hand, the Ktip showed constant value in the rage of 2∼3 MPa\sqrtm during the crack extension. With these results, the shielding effect, which is the relaxation mechanism of stress intensity, was experimentally verified.
