Analysis of Stable Crack Growth on the Basis of a Two-Criterion Approach

We propose a method for the analysis of stable crack-length increment Δa(where Δais regarded as a function depending on the parameters KIand σrof the two-criterion approach). It is shown that the KRcurve consists of two portions: {K′}Rand {K′ ′}Rcurves, which in the framework of the fracture evaluation diagram correspond to two portions of the loading curve – prior to and after its intersection with the limit curve of the fracture evaluation diagram. We propose an analytic description of the {K′}Rcurve as the first approximation, while the shape of the {K′ ′}Rcurve is shown to be fully determined by the limit curve of the fracture evaluation diagram. The method has been verified by using the experimental data of the ASTM Round Robin tests performed in 1979–1980 and predicting the maximum fracture load Pfof cracked specimens made of various materials: compact specimens, center-cracked specimens and special specimens with three holes. Good agreement between predicted and experimental data is demonstrated.