Non-Steady State Temperature Distribution and Thermal Stress History in Ceramic Disks Heated under Constant Heat Flux Conditions

Abstract

Temperature distribution of ceramic disks subjected to suddenly heating from outside under constant heat flux conditions was measured to estimate the thermal stress history and evaluate the first kind thermal shock resistance parameter of ceramic materials. Also, numerical calculations were conducted to compare with experimental data for each heating condition. Temperature dependence of thermal conductivity and thermal diffusivity was introduced into the calculation to realize the practical heat conductive condition. Two types of ceramics were used for the experiment; alumina ceramics having high and varying thermal conductivies and mica ceramics having low and constant thermal conductivities. As a result, it was found that the thermal stress history of heated disks is easily estimated from measurement of temperature distribution of the specimen. Temperature dependence of thermal properties was substantially affected on temperature distribution and thermal stress history, and it is shown that varying thermal properties in alumina ceramics can lead to a significant increase in the maximum tensile thermal stress generated in the center of the disks. As demonstrated by the numerical calculation for many kinds of other ceramics, maximum thermal stress of heated disks under constant heat flux condition shows non-steady-state value.