Two-parameter fracture criterion (K ρ,c -T ef,c ) based on notch fracture mechanics

Abstract

A two-parameter fracture criterion has been proposed to predict fracture conditions of notched components. This criterion includes the critical notch stress intensity factor K ρ,c, which represents fracture toughness of a material with a notch of radius ρ, and the effective T-stress. The effective T-stress T ef has been estimated as the average value of the T-stress distribution in the region ahead of the notch tip at the effective distance X ef . These parameters were derived from the volumetric method of notch fracture mechanics. The results of numerical T ef,c-stress estimation are compared to the T ef,c-stress results obtained from experimental analysis. The material failure curve or master curve K ρ,c = f(T ef,c) has been established as a result of the notched specimen tests. A large T ef,c range was covered from −0.80 σ Y to +0.19 σ Y using SENT, CT, RT (roman tile) and DCB specimens. It was shown that the notch fracture toughness is a linear decreasing function of the T ef,c-stress. The use of the material failure curve to predict fracture conditions was demonstrated on gas pipes with the surface notch.