Session: 06-04-01 Strain Capacity

Paper Number: 134215

134215 - A Novel Correlation Model Between the Critical CTOD and Crack Tip Constraint of High-Grade Pipeline Girth Weld 

Abstract: 

Under the action of external load, the crack driving force of the girth weld is greater than the fracture toughness of the material, which will lead to the fracture failure accident of the girth weld of the pipeline. As an important parameter of the failure limit state prediction model, the fracture toughness of the material is affected by the constraint state of the structural crack tip. Therefore, it is necessary to establish an accurate correlation between the fracture toughness of the material and the crack tip constraint. In this paper, based on the theory of meso-damage mechanics, a multi-scale numerical simulation model of crack propagation resistance of girth welds is established to accurately describe the complete fracture behavior of crack tip passivation, crack initiation and tearing. The test method of toughness resistance curve based on silicone rubber replication is carried out to further verify the accuracy of the numerical model. Based on this, the influence of material properties and geometric structure size on the toughness resistance curve of girth welds is proved. The results show that the yield strength has little effect on the toughness of the material. Increasing the strength matching coefficient of the weld, reducing the yield ratio of the material, and reducing the initial void volume fraction in the material can significantly improve the toughness of the material. The rationality of different crack tip constraint parameters to describe the correlation between fracture toughness and constraint is discussed. An accurate characterization method of crack tip constraint difference of weld metal based on the equivalent plastic zone area of crack tip is proposed. A unified correlation between the CTOD of girth welds and the crack tip constraint is established, which is suitable for different material properties. The accuracy of the established constraint-fracture toughness correlation is verified by the finite element calculation results of full-scale pipeline girth welds, and the average relative error is less than 4 %. The research results can provide theoretical guidance for the accurate determination of fracture toughness of pipeline girth welds in fracture evaluation.

Presenting Author: Dong Zhang China University of Petroleum (Beijing)

Presenting Author Biography: Dong Zhang, PhD candidate, mainly engaged in the research on oil and gas production equipment failure analysis, integrity management and intelligent pipeline.

Authors:

Dong Zhang China University of Petroleum (Beijing)
Hong Zhang China University of Petroleum ( Beijing )
Haonan Zhang China University of Petroleum ( Beijing )
Yue Yang China University of Petroleum ( Beijing )
Qingshan Feng China Oil & Gas Pipeline Network Corporation
Dongying Wang China Oil & Gas Pipeline Network Corporation
Chong Wang China Oil & Gas Pipeline Network Corporation
Xiaoben Liu China University of Petroleum ( Beijing )