Micro-structural reliability design of brittle materials

The paper analyses the effects of statistical distribution of micro-structural defect sizes concerning a scatter of brittle material fracture toughness. The results can be utilized for reliability assessment of selected engineering components operating under conditions of imminent brittle fracture. The reliability, taken as a complementary probability of brittle fracture initiation, is discussed, taking into account the character of the defect size statistical distribution, material mechanical properties, and varying loading and stress conditions of the component. Application of this method on Ni-Cr steel has demonstrated that there is very good agreement of the fracture behaviour predicted scatter with experimental results. This probability approach is compared with a deterministic reliability method originating from computations of safety factors. Its rational evaluation, as a function of the acceptable probability of fracture instability, provides a highly effective tool for designing of engineering components.