Characterisation of Ductile Crack Growth Behaviour Through a Novel Normalised P-ΔLL Master Curve

Abstract

This paper presents findings of fracture experiments and analyses obtained as part of research on stable crack growth behaviour in low alloy steel (EN 34NiCrMo6). Results of fracture tests conducted on CT specimens of low constraint (section slenderness ratio, b0/B ∼6), with various a0/W ratios and different loading angles, φ, are presented. Analysis of results revealed that the point at which behaviour departs from linearity (attributed to initiation of stable crack behaviour) is similar relative to maximum-recorded load, Pmax. The load-line displacement, ΔLL at Pmax, ΔPmax, was also found to be similar. An attempt was made thus at representing results of fracture tests, in terms of a normalised P-ΔLL curves. Normalised experimental plots have shown to represent a single “master” curve characterising stable crack growth behaviour. The proposed method was also applied to other experimental data in the literature on other materials and of other specimen configurations and loading modes. Comparisons do show that the experimental results reduce to a single trendline. The proposed normalisation therefore does provide promising results in characterising stable crack growth behaviour and can contribute greatly to the addressing of transferability issue of fracture tests of low constraint specimens.