Probabilistic fracture mechanics: J-estimation and ®nite element methods

The objective of this study was to evaluate the adequacy of current J-estimation models commonly used in probabilistic elastic±plastic analysis of ductile cracked structures. A newly developed probabilistic model based on elastic±plastic ®nite element method was used to evaluate the J-estimation model. In both models, the analyses involve elastic±plastic fracture mechanics for underlying deterministic calculations, statistical representation of uncertainties in loads, crack size, and material properties involving both tensile and fracture toughness characteristics, and standard computational methods of structural reliability theory. Numerical examples are presented for twoand three-dimensional cracked structures. The results show that the probabilistic analysis based on J-estimation model provides accurate estimates of failure probability when compared with those predicted by generally more accurate ®nite element model. The uncertainty in the crack size, if exists, can have a signi®cant e€ect on the probability of failure, particularly when the crack size has a large coecient of variation. A ®nite element-based probabilistic fracture-mechanics model is useful in benchmarking approximate results of J-estimation analysis. Ó 2000 Elsevier Science Ltd. All rights reserved.