Advancing fracture toughness evaluation: The Weighted Omega metric for enhanced sensitivity to Brittle-to-Ductile transitions and geometric variations

The brittle-to-ductile transition in metals underpins material safety and reliability in critical applications, such as aerospace, energy pipelines, and construction. This study introduces a Weighted Omega metric to address limitations in existing fracture characterization methods, particularly the Shear Area (SA) and the original Omega approach. While SA suffers from subjectivity and binary classification, and the original Omega lacks sensitivity to temperature, the Weighted Omega metric incorporates fracture surface curvature to capture the continuum from brittle to ductile characteristics. Using Drop Weight Tear Testing, the proposed approach was validated on three API steel grades across temperatures from 20 °C to −47 °C and specimen thicknesses from 19 to 33 mm. Results demonstrated a strong alignment of the proposed method with SA trends while revealing its enhanced sensitivity to variations in temperature, thickness, and fracture morphology.