Research on stress detection technology of long-distance oil and gas pipeline based on magnetomechanics characteristics

Magnetic memory stress detection technology has broad application prospects in the field of stress detection in long-distance oil and gas pipelines because it supports non-contact and dynamic on-line detection. However, the magnetic memory signal is weak and susceptible to an external magnetic field. A J-A model is established to quantitatively study the distribution characteristics of the magnetic memory signal in the stress concentration area of the pipeline. In this study, the mathematical model of magnetomechanics of the pipeline is established. The variation law of magnetic memory signal in the stress concentration area with the external magnetic field is calculated and analysed. A systematic experimental study is carried out. The results show that the magnetic memory signal linearly changes with stress in the geomagnetic field, and magnetic memory signal characteristics of circumferential stress with internal pressure is larger than the axial one. The amplitude of the magnetic memory signal in the stress concentration area increases with the increase in magnetic field intensity of the weak magnetic field, meantime the magnetic sensitivity decreases. The magnetic memory signal in the stress concentration area of the pipeline in magnetic saturation is covered by the strong magnetic field resulting in an undetected stress concentration area.