NUMERICAL EVALUATION OF PROBABILISTIC FRACTURE PARAMETERS USING WSTRESS

Describes a probabilistic methodology for fracture assessments of flaw ed structures constructed of ferritic steels using the research code W STRESS. The probabilistic formulation for cleavage fracture implements a multiaxial form of the weakest link model which couples the macrosc opic fracture behavior with a micromechanics model based on the statis tics of microcracks. The Weibull stress, sigma(w) emerges as a suitabl e near-tip parameter to provide a connection between the microregime o f failure and remote loading (J). WSTRESS builds on an iterative proce dure to incorporate a 3-D finite element description of the crack-tip stress field and measured values of fracture toughness to calibrate th e Weibull modulus, m, and the scale parameter, sigma(u), Specific feat ures of the code include statistical inference of Weibull parameters b ased on uncensored and censored models (with maximum likelihood method ), construction of confidence intervals, several definitions for the n ear-tip fracture process zone and other general facilities such spatia l integration of the stress field (to incorporate the random orientati on of microcracks) and stochastic simulation of fracture data using th e Monte Carlo method. The code also includes a convenient free-form co mmand language and a seamless interface with finite element results fi les stored in Patran binary or ASCII format.