APPLICABILITY OF PLASTIC ETA FACTOR SOLUTIONS IN J ESTIMATION PROCEDURES FOR TENSILE SE(T) FRACTURE SPECIMENS

This work investigates application of the eta-factor (which bears direct connection with laboratory toughness measurements) on accurate and robust estimates of J for clamped single edge notch tension (SE(T)) specimens made of homogeneous and welded materials using load-displacement records. Very detailed nonlinear finite element analyses for plane-strain models provide the evolution of load with increased load-line displacement and crack mouth opening displacement to define the applied load as a separable function dependent upon crack geometry, material deformation and mismatch level. The procedure enables determining the corresponding separation parameters for each specimen geometry thereby allowing evaluation of factor eta derived from a load separation analysis. The study shows that eta -factors based on load-displacement records defining the plastic area provide effective and accurate toughness measurements for clamped SE(T) fracture specimens. The analyses also revealed that eta -factors for clamped SE(T) fracture specimens based on load-line displacement (LLD) records and plastic area are relatively insensitive to weld strength mismatch. Overall, the present results provide a strong support to use eta-based procedures in toughness measurements using clamped SE(T) fracture specimens.