INITIATION OF CRACK FROM THE PORES IN CERAMICS UNDER THERMAL SHOCK ——Ⅰ: ANALYSIS OF THERMAL STRESSES

Cracking initiating from the surface of ceramics is a typical failure mode when the ceramic with high temperature is suddenly put into air or water with low temperature. So, the microstructure of the surface and near the surface of the ceramics is one of the dominant factors for the thermal shock behaviors of the ceramics. In other words, some experimental results have shown that porous ceramics manifested good thermal shock behaviors compared with dense ceramics, but the mechanism related to the fact has not been explained quantitatively. In the present paper, with the commercial finite element method (FEM) package, ABAQUS, stress distributions on and near the surface of the ceramics under sudden temperature change, particularly around the pores on the surface (open pores) and the pores near the surface (closed pores), were analyzed. It is found that the stress concentration caused by the closed pores was more serious than that caused by the open pores.