Let a material have a yield strength σ σ Y and a fracture toughness in mode I K I c . Based on fracture mechanics, the material will fail at stress σ σ fail = K I c / π π a . Based on plasticity, the material will yield when σ σ f a i l = σ σ Y . These curves intersect when a = K I c 2 / π π σ σ Y 2 . This value of a is called as transition flaw size a t ., and depends on the material properties of the structure. When the a < a t , the failure is governed by plastic yielding, and when a > a t the failure is governed by fracture mechanics. The value of a t for engineering alloys is 100 mm and for ceramics is 0.001 mm. If we assume that manufacturing processes can give rise to flaws in the order of micrometers, then, it can be seen that ceramics are more likely to fail by fracture, whereas engineering alloys would fail by plastic deformation.