Crack patterns corresponding to the residual strength plateau of ceramics subjected to thermal shock

The formation mechanism of the residual strength plateau of ceramics subjected to thermal shock is addressed. A set of thermal shock experiments of 99Al₂O₃ are conducted, where the thin specimens of 1 mm×10 mm×50 mm exhibit parallel through edge cracks, and thus permit quantitative measurements of the crack patterns. The cracks evolve with the severity of thermal shock. It is found that there is a correlation between the length and density of the thermal shock cracks. The increase of crack length weakens the residual strength, whereas the increase of crack density improves it. In a considerably wide temperature range, the two contrary effects just counteract each other; consequently a plateau appears in the variation curve of the residual strength. A comparison between the numerical and experimental results of the residual strength is made, and they are found in good agreement. This work is helpful to a deep understanding of the thermal shock failure of ceramics.