Numerical Study of Thermal Shock Damage Mechanism of Polycrystalline Ceramics

A dual-scale model is proposed to study the effect of microstructure parameters (grain size and grain boundary fracture energy) on the thermal shock damage mechanism on an example of alumina. At microscale, representative volume element (RVE) models generated by Voronoi tessellation are simulated to obtain the mechanical parameters for macro models. At macroscale, a coupled thermomechanical model based on the finite-discrete element method (FDEM) is applied to simulate the crack nucleation and propagation. Energy dissipation (ALLDMD) is introduced to investigate the thermal shock cracking mechanism by combining crack patterns and crack density, which indicates that decreasing grain size and increasing grain boundary fracture energy have a positive effect on thermal shock resistance. The proposed models not only predict the critical stress temperature which is well consistent to the theoretical thermal shock resistance factor, but also quantify the two previously unconsidered stages (crack nucleation and crack instability stage). Our models suggest the crack nucleation and instability will not occur immediately when the model reaches critical stress, but the models can sustain for higher temperature difference. The thermal shock damage mechanism and the influence of microstructural parameters on thermal shock resistance have also been discussed in detail.