WEIBULL ASSESSMENT OF CLEAVAGE FRACTURE FOR STEELS UNDER MIXED-MODE I AND II LOADING

Abstract

The increasing usage of high-strength steels in structural applications drives the development of quantitative cleavage fracture assessment for critical engineering materials. The observed large scatter in the experimentally measured fracture toughness values creates significant challenges in assessing the brittle structural failure through a conventional, deterministic approach often utilized to assess ductile fracture failure. The Weibull stress model has become widely acknowledged to characterize the statistical scatter of fracture toughness under pure mode I conditions. This study extends the Weibull stress framework into the mixed-mode I and II ductile-to-brittle transition (DBT) fracture. The present work investigates a universally acceptable stress-based failure criterion under the mixed-mode I and II loadings, and incorporates the ductile tearing effect into the extended Weibull stress framework. This study also encompasses an extensive experimental program for the high-strength steel material S550 under four-point bend and shear, mixed-mode I and II conditions.