Fracture response of 1422-mm diameter pipe with double-V groove weld joints and circumferential crack in fusion line. (September 2020)

• Record Type: Journal Article
• Authors: Wu, Kai; Liu, Xiaoben; Zhang, Hong; Sui, Yongli; Zhang, Zhenyong; Yang, Die; Liu, Yuqing
• Is Part Of: Engineering failure analysis. Volume 115(2020)
• Publication Date: 2020-09
• Subjects: Pipeline -- Girth weld -- Crack driving force -- Fracture behavior -- Finite element analysis; System failures (Engineering) -- Periodicals; Fracture mechanics -- Periodicals; Reliability (Engineering) -- Periodicals; Pannes -- Périodiques; Rupture, Mécanique de la -- Périodiques; Fiabilité -- Périodiques; Fracture mechanics; Reliability (Engineering); System failures (Engineering); Periodicals; Electronic journals; 620.112
• DOI: 10.1016/j.engfailanal.2020.104641
• Languages: English
• ISSNs: 1350-6307

Abstract

Highlights: A rigorous finite element model is developed. Influence of material property and loading condition on the J integral is analyzed. A new reference strain-based prediction formula is derived. Abstract: A circumferential crack in the fusion line is a major threat to the structural integrity of the pipeline girth weld because it may possibly lead to fracture failure when subjected to large plastic deformations. For the newly constructed X80 pipeline with an outside diameter (OD) of 1422 mm in China, the complicated configuration of welded joints and the outer diameter are outside the range of the general fracture assessment standards, such as BS 7910. Furthermore, during the pipe manufacture process, pipeline designers merely specify the minimum yield strength limit according to the pipe steel grade. This results in a wide variation range in the choice of yield strength values of the base metal. This also leads to a serious problem in the fracture assessment of pipe girth weld because the weld strength is commonly considered to be either evenly matched or overmatched. The foregoing factors make it difficult to perform an accurate fracture assessment using conventional standards. This study therefore aims to investigate the fracture behavior of 1422-mm OD pipelines with a double-V groove weld and circumferential crack in the fusion line. The specific effect of material mismatch and the realistic operational parameters that influence the fracture capacity of the pipe are examined via a series of numerical investigations. First, a rigorous three-dimensional finite element model to simulate the pipe girth weld is established by utilizing the ABAQUS finite element code package. The weld, which has a canoe-shaped surface crack in the fusion line between the heat-affected zone and root welding metal, is subjected to biaxial loading conditions. The keyhole method is adopted to simulate the crack front as well as the crack tip to eliminate the stress singularity effect during deformation. A refined mesh strategy is introduced to ensure the accurate simulation of the stress and strain fields in the vicinity of the crack tip. Based on the numerical model, the J-integral fracture parameter, which is clearly defined based on a strict mechanical theory, is chosen to characterize the effect of strength matching ratio, internal pressure, and yield to tensile strength ratio on the crack driving force. A new strain-based J-integral prediction formula is proposed based on numerical results.