Elastic-Plastic Fracture of Circumferential Through-Wall Cracked Pipe Welds Subject to Bending

A methodology is proposed to carry out elastic-plastic fracture analysis of through-wall cracked ductile pipe weldments subjected to pure bending loads. It is based on deformation theory of plasticity, constitutive law characterized by Ramberg-Osgood model, and an equivalence criteria incorporating reduced thickness analogy for simulating system compliance due to the presence of a crack in weld metal. Closed-form solutions are obtained in terms of elementary functions for approximate evaluation of energy release rate and center crack opening displacement. The method utilizes material properties of both base and weld metals which are not considered in the current estimation methods. It is general and can be applied in the complete range between elastic and fully plastic conditions. Numerical examples are presented to illustrate the proposed technique. Comparisons of results with reference solutions from finite element method indicate satisfactory prediction of foregoing fracture parameters.