Simulation of the thermal shock behavior of ultra-high temperature ceramics with the consideration of temperature-dependent crack propagation criterion and interaction between thermal shock cracks evolution and thermal conduction

Abstract

The constitutive relation of micro-cracked ultra-high temperature ceramics deduced by energy method and the temperature-dependent critical energy release rate of ceramics were demonstrated in this paper. Taking advantage of the constitutive relation and temperature-dependent critical energy release rate, the thermal shock behavior of Al2O3 had been simulated firstly with finite element method. Results showed that the crack patterns of simulation approximated in the experiments. That confirmed the accuracy of our model. The ZrB2-based ceramic was then used as an example to study the effects of the temperature dependence of crack propagation criterion on the evaluation of thermal shock resistance of ultra-high temperature ceramics. In addition, given that the cracks forming during thermal shock lead to discontinuities in the ceramic material and influence thermal conduction. The interaction between thermal shock cracks evolution and thermal conduction, and the corresponding effects on the thermal shock behavior of ultra-high temperature ceramics were studied for the first time. Results indicated that the thermal shock crack patterns and temperature fields were significantly different while the thermal conductivities at the cracks were different for identical thermal shock conditions. Therefore, in order to improve the accuracy of simulation and the evaluation of thermal shock resistance of ultra-high temperature ceramics, the temperature dependence of the crack propagation criterion and the interaction between the cracks evolution and thermal conduction must be taken into consideration.