Effect of Spatially Varying Thermal Conductivity on the Magnitude of Thermal Stress in Brittle Ceramics Subjected to Convective Heating

The effect of a spatial variation of the thermal conductivity on the magnitude of the maximum tensile thermal stress in a solid circular cylinder subjected to sudden convective heating was calculated by finite element methods. The general results show that by lowering the thermal conductivity in the surface region of the cylinder, the magnitude of the maximum tensile thermal stress at the center of the cylinder is reduced significantly. The negative temperature dependence of the thermal conductivity in dielectric materials, which indirectly creates a spatial variation in thermal conductivity, also causes a significant decrease in the magnitude of the tensile thermal stresses, as demonstrated by a numerical example for aluminum oxide. It is also shown that a spatial variation in thermal conductivity can significantly affect the time to maximum tensile stress as well.