Abstract
Fracture toughness data relevant to the thickness of the particular structure is beneficial to the advanced levels of fitness-for-service assessments. Out-of-plane constraint loss associated with the thickness effect was investigated using finite element analysis and fracture experiments on the edge cracked fracture mechanics samples of different thicknesses and crack length. It was shown that samples with deep cracks are significantly affected by the thickness, while the effect is smaller for samples with shallow cracks where the in-plane constraint effects are dominant. The fracture toughness Jc was dependent on the specimen thickness with thin specimens having a higher fracture toughness compared to the thick specimens. The out-of-plane effect in deep cracked samples was shown to be similar to the in-plane effect in shallow cracked samples.