Weak magnetic forward modeling of pipelines based on non-uniform distribution of stresses

During the operation of long-distance oil and gas pipelines, the pipeline wall is very prone to stress concentration under the continuous action of complex loads. Weak magnetic internal detection can detect stress concentration during the service of the pipeline, which has significant advantages in the diagnosis of pipeline stress damage. However, the traditional weak magnetic detection forward model mostly adopts the assumption of uniform stress distribution, which is difficult to accurately characterize the actual non-uniform distribution state of the stress concentration zone, resulting in theoretical deviations in the magnetic field characterization. Therefore, this study applies the finite element simulation platform to construct a three-dimensional model of X70 pipeline containing prefabricated defects to obtain the stress distribution at the defects. And based on the magnetoelastic effect, the coupling relationship model between stress distribution and magnetization intensity is constructed, and the magnetic charge density is used as a bridge to combine with the magnetic charge theory to establish a kind of weak magnetic detection forward model under non-uniform stress field, through which the influence of defect depth on the weak magnetic signals is systematically investigated, which provides a theoretical basis for the pipeline stress assessment.