The Characteristic Stress between Two Kinds of Delayed Failure for Ceramics at Elevated Temperature
The delayed failure behavior of ceramics is characterized with stress rupture and crack extension experiments. A linear relationship is evident between stress rupture data in higher applied stress level, denoting that the failure of material in this stress level is controlled by SCG. A evident deviation appears when extrapolating the straight line from higher stress level to lower stress level, implying a change in mechanism for failure. The characteristic stress value, σ0 ,for discerning between different stress regions in high temperature rupture can be calculated with SCG threshold, Kth. Calculated result is consistent with the measured result of stress rupture. Finally, a criterion for distinguishing between two mechanisms for delayed failure, SCG and creep rupture, with an intrinsic parameter of material, Kth, is obtained.
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