Numerical simulation of stress intensity factor at axial through-wall crack tip of pipeline

Crack is a common defect form in pipelines, and its stress intensity factor is an important basis for safety evaluation of pipelines. In order to accurately acquire the stress intensity factors of cracks in pipelines, the finite element model for solving the stress intensity factors of axial through-wall cracks in long-distance pipelines was established by 1/4 node method. The reliability of the new model was verified by comparing the stress intensity factors acquired by the finite element method and the analytical method. The effects of internal pressure, crack length, inner diameter and thicknessdiameter ratio on the stress intensity factor at the crack tip were studied, and the variation law of stress intensity factor along the wall thickness was studied. The results show that the rise in internal pressure and crack length will increase the stress intensity factor, while the increase of inner diameter and thickness-diameter ratio will decrease the stress intensity factor. However, the stress intensity factor will not change with the increase of diameter when the inner diameter exceeds 500 mm. The stress intensity factor at the outer wall of the pipeline is always higher than that at the inner wall. With the rise in internal pressure, cracks will be initiated from the outer wall of the pipeline. The calculation of stress intensity factor at crack tip based on 1/4 node method, which is easy to operate and high in calculation accuracy, can provide reference for safety evaluation of long-distance pipelines.