Thermal shock strength of Al2O3 by laser irradiation method

Various structural ceramics have been developed as heat-resistant materials. It is very important to investigate their thermal shock characteristics. This report presents a newly developed, laser irradiation method to evaluate thermal shock strength and proposes that a critical power density can be a new measure to evaluate heat resistant materials. The temperature and thermal stress distributions of the cylindrical shaped Al2O3 ceramics under irradiation by CO2 laser beams are analysed using FEM. The maximum tensile and compressive stresses are obtained with respect to beam diameters for various power densities. These relations lead to critical power densities at which materials are fractured. The relationships between the critical power density and beam diameters derive critical fracture curves which gives the fracture criterion of ceramics. Finally, the irradiation experiments were carried out and their results got a good agreement with the theoretical fracture criterion. It was concluded that the critical fracture curve can be a new measure to evaluate thermal shock resistance of ceramics. (C) 2001 Elsevier Science Ltd and Techna S.r.l. All rights reserved.