A NEW METHOD TO EVALUATE THE THERMAL-SHOCK RESISTANCE OF CERAMICS BY LASER-PULSE IRRADIATION

Structural ceramics are attracting attention in the development of nuclear fusion reactors because they have excellent wear- and heat-resistant characteristics. Ho wever, in some applications, they will be exposed to very high temperature and high-heat-flux environments. These ceramics are also subjected to thermal loadings that change rapidly with time. Therefore, it is important to investigate their thermal shock characteristics. A new approach to evaluate the thermal shock resistance of structural ceramics is based on laser pulse irradiation on the ceramic surface. The temperature and thermal stress distributions of cylindrical ceramics under irradiation by laser beams are discussed by using the MARC finite element computer code with arbitrary quadrilateral axisymmetric ring elements. The relationhship between the spot diameter of the laser beam and the maximum compressive thermal stress is derived for various power densities of the laser beams. A critical fracture curve is obtained from these relationships that beam spot diameter. The irradiation experiments are done on a machine ceramic by using a CO2 laser. Finally, theoretical results are compared with experimental ones. Both results show good agreements. Consequently, this method can be a new standard thermal shock test instead of the water quench test that has been used widely.