Measurement and modelling of R-curves for low-constraint specimens

R-curve testings of Grade X65 pipeline steel girth weld for low-constraint specimens were investigated experimentally. Single-edge-notched bending (SENB), single-edge-notched tension (SENT) and central-cracked tension (CCT) specimens were used to measure R-curves using the unloading compliance method. The recently developed single specimen unloading compliance for SENT specimens was validated using the multiple specimen method. Based on the test results, three constraint parameters (T-stress, Q-stress and A2) were used to derive constraint-dependent R-curves. A comparison of the predicted constraint-based R-curves against the test result was given. It is shown that all three constraint parameters can be effectively used for obtaining R-curves under low-constraint levels. The modelling method can potentially be used for engineering critical assessment (ECA) in various industry sectors.