Interference study of double cracks on the inner surface of pipe bends with axial misalignment weld defects

• Published in: Theoretical and applied fracture mechanics 2024-10, Vol.133, p.104526, Article 104526
• Main Authors: Tan, Dongmei, Tao, Yu, Gan, Qinlin, Ji, Baifeng, Luo, Hao, Li, An
• Format: Article
• Language: English
• Subjects: Double crack; Fracture mechanics; Mutual interference; Stress intensity factor
• ISSN: 0167-8442
• DOI: 10.1016/j.tafmec.2024.104526

•A model of natural gas elbow with axial misalignment weld defects is established.•The interaction between the elbow and the double cracks at the weld was studied.•The interference rules of different types of multiple cracks are analyzed. In engineering practice, erosion wear cracks in pipelines occasionally exhibit a phenomenon of multiple crack aggregation. To investigate the effect of the interaction between double cracks in natural gas pipelines with axial misalignment welds, this paper, based on fracture mechanics, firstly establishes a model of an external axial misalignment weld bend. By analyzing the double-crack model of the main crack and subsidiary crack, the interference effect of the subsidiary crack on the leading edge of the main crack is studied. The results show that when both the main crack and the accessory crack are annular cracks, all the points on the leading edge of the main crack are within the shielding zone of the accessory crack under the condition of co-linear neighboring position. Meanwhile, under the condition of coaxial neighboring position, all the points on the leading edge of the main crack are partly within the shielding zone of the accessory crack and partly within the reinforcing zone. Conversely, when the main crack is an annular crack and the accessory crack is an axial crack, the conclusion is opposite to the former. This study can provide a theoretical basis for the safety evaluation of multi-cracked gas pipelines.