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Damage and Failure Analysis of Ultra-High Temperature Ceramics (UHTCs) Subjected to Thermal Shock



In this study, the finite element analysis (FEA) software ABAQUS 2020 and the eXtended Finite Element Method (XFEM) were used to predict the crack initiation and propagation within a UHTC subjected to cold thermal shock from 2000°C to 20°C. Within the XFEM enriched region, the maximum principal stress damage criterion was implemented to capture the crack initiation, and an energy-based damage criterion was used for crack propagation. Two simulations were developed, one for zirconia diboride (ZrB2) and one for hafnium diboride (HfB2). Temperature-dependent thermomechanical and fracture material properties were used for both simulations. A convective heat transfer condition was applied to the models' exposed surface. The multiple crack initiation and propagation were captured by using several XFEM enriched regions. The results for both UHTCs showed that crack initiation began at the exposed surface of the geometry and propagated into the material in a fast and brittle manner. The study found that defining the UHTCs' material temperature-dependent properties for the cold thermal shock models produced faster cracking due to the embrittlement of the materials' elastic properties and the degradation of the fracture properties at high temperatures. The properties of the materials can be seen to degrade as the temperature increases.


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