An engineering approach to assess constraint effects on cleavage fracture toughness

This study presents a simplified approach to parameterize constraint effect s on the fracture toughness of ferritic steels in the ductile-to-brittle tr ansition (DBT) region under plane strain, small-scale yielding conditions f or non-zero T-stress. The Weibull stress serves to couple near tip and glob al loading which enables scaling of macroscopic toughness values across var ying constraint levels. Extensive finite element analyses then provide the relationship of F vs, T/sigma (0), where F = K-Jc(T not equal0)/K-Jc(T=0), in closed form for four typical ferritic steels. Given the non-dimensional F-function for a material, the scaling of fracture toughness values for con straint loss involves only simple function evaluations, making the method s uitable for use in more global simulations of fracture events, e.g. paramet ric studies to exam a wide range of crack sizes, locations and loadings. Th e paper describes several possible applications of the F-function model to correct toughness data for constraint loss, including shifts of the DBT ref erence temperature, T-0, for the material determined according to ASTM E-19 21. Comparisons of model predictions of DeltaT(0) are made with those deter mined from measured toughness data for an A515-70 steel. (C) 2001 Elsevier Science Ltd. All rights: reserved.