PROCESS ZONE SIZE FAILURE CRITERION AND PROBABILISTIC FRACTURE ASSESSMENT CURVES FOR CERAMICS

Data of fracture toughness and fracture stress of ceramics, generally show considerable size effects and scatter. This presents problems for the integrity of structural ceramics. Fracture mechanics test results on Si3N4 and A12O3 reveal a sensitivity to crack size and the necessity to invoke probabilistic concepts to evaluate their integrity. A new failure criterion is proposed here, based on the existence of a crack-tip process zone. A probabilistic failure assessment curve is also proposed to quantitatively evaluate reliability.