K(IC) MODELING FOR A CRITICAL STRAIN CRITERION INVOLVING THE STRESS TRIAXIALITY EFFECT

Abstract

An analytical model for predicting fracture toughness K(IC) is proposed based on a stress-modified critical strain criterion, that reflects the effect of stress triaxiality on ductile fracture. For K(IC) modelling, the notch-tip strain and stress states are given by introducing a singular field for the case of power-law-hardening materials. Notch fracture toughness is interpreted in terms of the notch-root radius (rho): K(IC) is predicted to increase with increasing rho, but has a minimum at a small rho. The microstructurally characteristic distance and the reference critical strain can be estimated by fitting the K(IC) vs rho data on the model equation. Finally, previous notch fracture-toughness data are re-analyzed with the proposed model: the current analysis explains well the interaction effect between the notch-tip strain field and the local-fracture-controlling microstructure even in the small rho range.