A Modified Weibull Stress Approach to Predict Specimen Geometry Effects in a Pressure Vessel Steel

摘要

This work describes a modified Weibull stress (σ_w) approach incorporating the potentially strong effects of plastic strain on cleavage fracture. The primary purpose of this study is to explore application of a probabilistic-based micromechanics model incorporating effects of plastic strain on cleavage fracture to determine the reference temperature for pressure vessel steels from precracked Charpy (PCVN) specimens. Fracture toughness tests conducted on an A515 Grade 65 pressure vessel steel provide the cleavage fracture resistance data needed to assess specimen geometry effects on J_c-values. Calibration of the modified Weibull stress parameters provides the relationship between σ_w and macroscopic load (in terms of the J-integral) from which the variation of fracture toughness across different crack configurations is predicted. For the tested material, the modified Weibull stress methodology effectively removes the geometry dependence of fracture toughness.