The role of the second non-vanishing terms in the material failure curve on APL 5L steel

Purpose: It is now well-known in the fracture-mechanics community that a single fracture parameter alone may not be adequate to describe crack-tip condition. To address this problem, there has been a recent surge of interest in crack-growth behaviour under conditions of low crack-tip stress triaxiality. This paper exploited the K-A3 crack approach, which was derived from a rigorous asymptotic solution and has been developed for a two-parameter fracture. Design/methodology/approach: The material failure curve or master curve, has been established as a result of the notched specimen tests. It was shown that the notch fracture toughness is a linear decreasing function of the stress. The use of the material failure curve to predict fracture conditions was demonstrated on gas pipes with the longitudinal surface notch. Findings: No finding. Originality/value: This approach requires that the constraint in the test specimen approximate that of the structure to provide an “effective” toughness for use in a structural integrity assessment. The appropriate constraint is achieved by matching thickness and crack depth between the specimen and structure.