Multiscale modeling for the simulation of damage processes at refractory materials under thermal shock

Refractory materials contain defects such as voids, microcracks or grain boundaries. Being exposed to high temperature gradients, strength and lifetime are essentially determined by these microscopic features. Bringing forward the understanding of micro–macro interactions, simulating damage patterns and predicting lifetime of refractory structures, a micromechanical damage model for thermomechanical dynamic loading conditions is presented. The material laws are formulated on the continuum level using appropriate homogenization methods. To combine fracture- and damage-mechanical approaches, submodels containing sharp crack tips are introduced at the ends of the damage zones. Also, conservation contour integrals are applied to damage zones yielding the energy release rates of equivalent crack configurations. Finite element simulations are presented showing wedge splitting tests exhibiting an extended R-curve behavior and cyclic thermal shock tests giving insight into evolving damage patterns. To quantify the thermal shock resistance of refractory ceramics, experiments suggested by Hasselman are simulated numerically supplying critical temperature slopes.