Weak Magnetic Signal Characteristics for Critical Damage of Oil and Gas Pipelines Based on Electron Spinning

Stress and deformation are important factors that affect the safe operation of pipelines. Plastic deformation in the pipeline indicates a state of critical damage. Based on micro-magnetization and stress equivalent magnetic field theories, the change mechanism of ferromagnetic materials under external stress is analyzed. The 3D simulation model of the iron–carbon alloy system is established by the Material Studied software, and the relationship between the system magnetism and stress is obtained by calculating the electronic spin state distribution changes under different stress applications. The pipeline suppression experiment is designed to study the change characteristics of the magnetic induction intensity on the pipeline surface during the repeated suppressions until yield. Results show that the weak magnetic signal continuously varies as the pressure on the pipeline increases. The greater the pressure, the lower the magnetic induction intensity on the pipe surface. The pipeline exhibits different weak magnetic signal characteristics in the elastic and plastic deformation stages. The magnetic signal variation curve has apparent inflection points. The deformation and damage states of the pipeline can be assessed by the change characteristics of the weak magnetic signal. Repeated suppression causes the pipeline magnetism to weaken and the initial magnetization of the material to decrease. The experimental results are consistent with the theoretical analysis.