Study on Internal Detection in Oil–Gas Pipelines Based on Complex Stress Magnetomechanical Modeling

The pipeline stress internal detection technology is an international frontier subject in the field of pipeline internal detection, in which the micromagnetic method has a great application potential. However, the pipeline micromagnetic stress internal detection technology lacks an effective theoretical model as a scientific guide due to the complex stress distribution inside the pipe wall during the operation of the pipeline. In this article, based on the complex stress magnetomechanical coupling model, we have studied the corresponding relationship between the stress and the micromagnetic signal and analyzed the influence of the external magnetic field on magnetomechanical relationship under the nonmagnetic saturation condition. And the correctness of the theoretical model is proved by systematic experimental research. The results indicate that the stress has a one-to-one linear relationship with the micromagnetic signal in the stress concentration region. The error rate between the theoretical calculation result of the uniaxial stress magnetomechanical coupling model and the experimental result is 89.4%, and the error rate between the theoretical calculation result of the complex stress magnetomechanical coupling model and the experimental result is 0.5%, which proves that the complex stress magnetomechanical coupling model established in this article is more suitable for the data analysis of the pipeline stress detection. Further, the force magnetic change rate and the micromagnetic signal in the stress concentration region increase with the increase of the external magnetic field intensity in the nonmagnetic saturation state.