Experiment and numerical simulation of stress detection for oil and gas pipelines based on magnetic stress coupling of pipeline steel

Abstract

In this study, a stress detection method is proposed to address the challenge of developing a nondestructive stress testing technique for oil and gas pipelines in real-time and online due to the complexity of the service environment and particularity of the transportation medium. The method is based on the magnetic mechanical properties of pipeline steel materials and the magnetic induction intensity stress coupling relationship. To evaluate the proposed method, six commonly used pipeline steels (X52, X56, X60, X65, X70, and X80) were selected as research objects, and their hysteresis curves were tested. The local magnetization key parameters of oil and gas pipelines were determined based on their magnetic properties. In addition, a finite element simulation model was established for oil and gas pipelines with coupling of magnetic field and stress field. This study appraise the distribution of magnetic field and magnetic induction intensity along the length and cross section height of the oil and gas pipelines simulation model after local magnetization, without being pressurized. Moreover, it examines the mechanism of magnetic induction intensity and stress variation of the simulation model under different internal pressures of the oil and gas pipelines. To this end, a coupling relationship of axial stress, circumferential stress, and magnetic induction intensity was separately established. Moreover, stress–strain test and magnetic induction intensity test systems were integrated to test the X80 pipeline steel. Through analyzing the test data and finite element simulation data, the validity of magnetic coupling simulation of oil and gas pipelines and the reliability of stress detection were verified. The results provide a theoretical basis for the key technologies of nondestructive online stress detection of oil and gas pipelines.