A constraint-based approach for notch cleavage fracture toughness estimations

•Novel Notch Constraint Method: J-Q approach for effective material toughness evaluation.•Calibrated & Validated: Experimental data used to validate methodology's accuracy.•Increased Fracture Toughness: Significant rise in estimated effective notch fracture toughness.•Weibull Model for Flexibility: Incorporates conservatism adjustment for assessments.•Versatile Application: Potential for broader use in diverse materials and geometries.