Thermal Shock Resistance and Fracture of Ceramic Materials

Abstract

In this report we discuss the results of theoretical and experimental methods developed for estimating the thermal stress state of finite bodies having single and multiple cracks. We consider how the above-mentioned factors effect the fracture Kinetics and bearing ability of thermally loaded ceramics. Using nonstationary thermal shock methods, e.g. axisymmetric heating or cooling the outer surface of cylindrical bodies in liquid media, plasma or electron-beam heating of a cylinder top, it is shown the fracture character changes from appearance of some cracks resulting in a partial loss of bearing ability to a complete body fracture. According to the extent of the compression and tension areas in a body and the stress relation in these areas the relative thermal stress resistance of elastic and brittle ceramic materials may vary from tensile strength values to compressive strength ones. It is shown on the basis of linear fracture mechanics concepts that in the general case for estimating the bearing strength of a thermally loaded body it is necessary to take into consideration the history of loading and fracture kinetics in view of the stress redistribution in the whole volume of a finite body at the intermediate stages of cracks development and interaction.