Session: 06-04-01 Strain Capacity

Paper Number: 134238

134238 - Experimental and Numerical Investigation of Failure Criterion of Girth Welds With I-II Mixed Mode Crack Considering Crack Tip Constraint Effect 

Abstract: 

In practical engineering scenarios, cracks predominantly manifest in mixed mode configurations, presenting a complex challenge for pipeline girth welds characterized by discontinuous geometry and nonlinear material properties. The establishment of a robust fracture criterion for girth welds featuring mixed mode cracks has become pivotal for ensuring pipeline safety. To account for the influence of shear deformation of micro-voids, the shear modified Gurson-Tvergaard-Needleman (GTN) model for girth welds was determined. Compact-tensile-shear (CTS) tests, employing digital image correlation (DIC) technology, were conducted to precisely calibrate the damage parameters within the shear modified GTN model. Employing finite element numerical calculations, the study analyzed the effects of material damage parameters, material mechanical properties parameters, and size parameters on the constraint state of the crack tip, resistance curve of mixed mode cracks, and fracture toughness of CTS samples. The area enclosed by the plastic strain contour (Ap) at the crack tip was utilized to characterize the constraint state of the crack tip, while the crack tip opening displacement (CTOD) and J-integral were employed to characterize the crack fracture parameters. The results indicate that the CTOD resistance (CTOD-R) curve of I-II mixed-mode crack, the J-integral resistance (J-R) curve of I-II mixed-mode crack, the fracture toughness of CTS samples, and the Ap at the crack tip decrease with the increase of the initial void volume fraction, shear damage coefficient, and specimen thickness, and increase with the rise of the strength matching coefficient. The softening rate of the heat-affected zone has little effect on the CTOD-R curve of I-II mixed-mode crack, the J-R curve of I-II mixed-mode crack, the fracture toughness of CTS samples, and the Ap at the crack tip. Similarly, the yield-to-tensile strength ratio of the base metal has little effect on the J-R curve of I-II mixed-mode crack, the fracture toughness of CTS samples, and the Ap at the crack tip. However, the CTOD-R curve of I-II mixed-mode crack increases with the increase of the yield-to-tensile strength ratio. Furthermore, a linear correlation between the constraint state of the crack tip and the fracture toughness of CTS samples was established. Leveraging a neural network regression prediction algorithm, a data-driven prediction model for the fracture toughness of girth welds with I-II mixed mode cracks was proposed. This research serves as a valuable reference and guide for the analysis of fracture behavior and safety evaluation of pipeline girth welds with I-II mixed mode cracks.

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:

Yue Yang China University of Petroleum ( Beijing )
Hong Zhang China University of Petroleum ( Beijing )
Han Zhang China University of Petroleum ( Beijing )
Dong Zhang China University of Petroleum (Beijing)
Pengchao Chen PipeChina Institute of Science and Technology
Bingchuan Yan China Oil & Gas Pipeline Network Corporation
Hao Wang China University of Petroleum ( Beijing )
Xiaoben Liu China University of Petroleum ( Beijing )