Size effect of thermal shock crack patterns in ceramics and numerical predictions

The present work examines the size effect of thermal shock crack patterns in ceramics and develops quantitative predictions. A set of water-quenching experiments on thin ceramic specimens of different widths yielded two-dimensional, periodic and hierarchical readings of thermal shock crack patterns, which showed the strong size-dependence of the crack length and length hierarchy, and the size-independence of the crack spacing. Furthermore, the effective convective heat transfer coefficients inversely estimated from the crack spacing data were observed to be size-independent. Such a finding may help engineers to assess the thermal shock failure of practical ceramic components by designing specimens of standard size. Numerical simulations were conducted and the results are in good agreement with experimental data. Several interesting phenomena of the evolution of thermal shock crack patterns were revealed and discussed. The present study has led to a much improved scientific understanding of thermal shock cracking phenomenon of ceramics.