Application of WES2808 to Brittle Fracture Assessment for High Strength Gas Pipelines

This paper presents the results of a preliminary study to establish an assessing method for the tensile strain limit against brittle fracture of pressurized gas pipelines subjected to axial tensile deformation. The basis of the assessment method is the Japan Welding Engineering Society standard WES2808–2003. WES2808 provides a procedure for evaluating the fracture limit using the CTOD design curve relating flaw size, applied strain and fracture mechanical parameter (CTOD). The main characteristics of the method are a consideration of the deterioration of the fracture toughness of material resulting from large cyclic and dynamic straining, a correction of CTOD fracture toughness for constraint loss in structural components in large scale yielding, and an estimation of critical CTOD value from Charpy test results. Modifications of the procedure to enable evaluation of the fracture properties of high strength gas pipelines under biaxial loading conditions are studied.