Study on Fracture Toughness Evaluation Using Small Specimen Based on the Master Curve Approach

This study focuses on clarifying an appropriate method for evaluating fracture toughness using a small-scale compact specimen.  The size effect on fracture toughness was analyzed by 3D-FEM from the following two points of view; one is in-plane size effect on crack-tip stress fields, and another one is specimen thickness effect on stress fields along crack front which could induce statistical effect on fracture toughness.  From these analytical studies, limit in-plane size that produces the same crack-tip stress fields as those in standard toughness specimen was discussed.  Moreover, method for correction of thickness effect on fracture toughness was proposed on the basis of the statistical fracture criterion, Weibull stress criterion, where the fracture driving force that provides material toughness independent of specimen size was employed.