Various structural ceramics have been developed as heat-resistant materials. In some applications it is anticipated that they will be exposed to very-high-temperature environments of the order of thousands of degrees. Moreover, these ceramics are subjected to thermal loadings which change rapidly with time. Therefore, it is very important to investigate their thermal shock characteristics. In this report, the distributions of temperatures and thermal stresses of cylindrical-shaped Al_2O_3 ceramics under irradiation by laser beams are analyzed using the finite element method. Critical fracture curves are obtained from the relationships between spot diameters of laser beams and maximum values of thermal stresses for various power densities of laser beams. The irradiation experiments yield these critical fracture curves, and theoretical and experimental curves are in good agreement.
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