Test Protocol Definition to Measure Fracture Toughness J-Parameter Using Non-Standard Four-Point Bending Specimens

This work proposes a new test methodology to characterize the fracture toughness values for either brittle or ductile materials, such as steels of risers and pipelines used in the oil and gas industry by using non-standard four-point bending specimens. Four-point bending (4PB) specimens show to be reliable configuration to characterize fracture toughness values. The methodology involves obtaining compliance equations, stress intensity factors, the proportionality factors between the deformation energy and J-integral, known as η-factor. This study evidences the impact of geometry variation on the crack-tip constraint. Laboratory tests were performed with four-point bending specimens. These experiments were compared with experimental data of standardized geometries SE(B) and SE(T). The results from the preliminary experimental campaign validated the numerical analysis. Thus, the proposed equations can be used to obtain the fracture toughness values using four-point bending specimens.