Strain-based J-estimation scheme for fracture assessment of misaligned clad pipelines with an interface crack

A reference strain J-estimation formulation is developed to perform the fracture assessment of misaligned clad pipelines containing a circumferential part-through crack located at the interface of weld metal and outer pipe. An extensive parametric study including a total of 896 finite element (FE) models is carried out to investigate the effects of various parameters (pipe diameter, crack depth, crack length, centreline offset, strength mismatch level, and strain hardening exponent) on the J-integral. Then, the estimation formulation characterizing the linear relationship between the J-integral and the applied displacement loading is proposed using the standard least square fitting, and a goodness of fit for the J-integral values obtained from the formulation and the FE analysis is endorsed. Finally, the application range of the estimation formulation is mostly extended by conducting further comparative study.