MAXIMUM THERMAL-STRESS IN CERAMICS WITH TEMPERATURE-DEPENDENT THERMAL-CONDUCTIVITY UNDER RAPID HEATING OR COOLING

Though numerous equations of the maximum thermal stress on ceramics have been proposed, many of them are only applicable to ceramics whose thermal properties are constant. In this paper, a numerical analysis of the maximum thermal stress in ceramics is carried out by accounting for the temperature dependency of the thermal conductivity. Correlative equations of maximum thermal stress are proposed using the Biot number and a parameter related to the thermal conductivity. The temperature dependency of thermal conductivity is found to contribute more to the maximum thermal stress under rapid cooling conditions than under rapid heating conditions. Further, the temperature dependency is found to have the greatest effect most when the Biot number is 2.3. Thus, in the water quench test, one must consider the temperature dependency of ceramics for a material with high temperature dependent thermal conductivity such as Al2O3.