A sequentially coupled mathematical thermal-stress model, based on the commercial finite-element code ABAQUS, has been developed to rationalize crack defect formation in fused cast alpha beta-alumina refractories used in the glass industry. The thermal model was validated against thermocouple and pyrometer measurements obtained in an industrial setting. The temperature predictions obtained from the thermal model were employed as input to the elastic strain-rate-independent plastic stress model. The constitutive behavior of alpha beta-alumina has been determined over a range of temperatures for input to the stress model. The distribution of beta-alumina that forms in the center of the casting due to rejection of Na_2O during solidification was introduced in the stress model through a user-defined subroutine in order to account for the effect of differences in the thermal contraction behavior and elastic modulus of the alpha beta- and beta-alumina phases. The stress analysis indicates that temperature gradients as well as the different dilatational behavior of the alpha beta- and beta-alumina phases are the main drivers of stress and strain evolution during solidification and subsequent cooling. The beta-alumina core, in particular, plays an important role in the generation of tensile stresses and likely gives rise to the generation of the internal cracks observed in industrial castings.
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