RESEARCH STATUS AND PROGRESS IN FRACTURE ASSESSMENT OF PIPELINE UNDER THE CONDITION OF LARGE-SCALE YIELDING

With the application of high-strength and high-toughness pipeline steel, relevant fracture assessment is needed for pipeline under large-scale yielding condition. This article summarizes limitations that govern the conventional fracture mechanics when applied to the fracture assessment of pipeline under the condition of large-scale yielding. Here, progresses in pipeline fracture assessment under the condition of large-scale yielding are presented in detailed in four main aspects: two-parameter fracture mechanics, constraint-corrected fracture toughness test, strain-based fracture assessment, and strain-based failure assessment diagram. First of all, two methods for constraint-corrected fracture toughness test are discussed, which is SENT specimen and apparent fracture toughness method. The research status and existing problem are reviewed for constraint-corrected fracture toughness test based on SENT specimen. The basic principles of strain-based fracture assessment are presented. The strain-based driving force equation and the CTOD failure criteria are introduced in the method of strain-based fracture assessment. Finally, an overview is given for the strain-based J-integral estimation and strain-based failure assessment diagram. Finally, key topics for further studies are pointed out.