Simulation And Experimental Research Of Oil And Gas Pipeline Stress Detection Signal Based On Magnetic Memory

With the rapid development of the national economy and the uncertainty of global energy industry brought by regional conflicts,the country attaches great importance to the energy industry,and energy transportation is becoming more and more important.Long-distance oil and gas pipeline is an important part of oil and gas transportation,but in the transportation process,due to external environmental factors and pipeline fatigue,stress concentration and even crack formation,these factors may cause oil leakage,and in serious cases,pipeline explosion,bringing inestimable losses.Therefore,the stress detection of the pipeline has become an essential part.At present,conventional stress concentration detection techniques for oil and gas pipelines include ultrasonic method,ray method,magnetic particle method,eddy current method and magnetic memory method,among which metal magnetic memory detection technology can carry out internal stress detection for in-service pipelines.As a kind of stress detection technology,magnetostriction effect occurs at stress concentration position when ferromagnetic workpiece is affected by geomagnetic field and load,and the magnetic domain is reoriented.The magnetic state of the metal surface remembers the location of stress concentration and other information,and the magnetic signal can be detected by the detector for analysis.The stress distribution around the crack is analyzed by finite element method.The relationship between stress and permeability is calculated by force magnetic coupling.The generation mechanism of magnetic memory signal is analyzed.The influence of different wall thickness,pipe diameter and load on the stress intensity of crack on the pipe is analyzed,and the influence of the lifting value of detection signal,stress intensity and stress direction on the characteristics of magnetic memory signal is studied,which provides a theoretical basis for magnetic memory detection technology.The results show that in the elastic range,when the external magnetic field intensity of ferromagnetic materials is unchanged,the magnetic induction intensity of ferromagnetic materials will change to some extent under the action of external force,and the magnetic permeability can be used as a bridge connecting mechanical simulation and magnetic simulation to simulate magnetic memory signals effectively.The magnetic memory signal characteristics decrease exponentially with the increase of detector lift value.When the pipe diameter increases,the stress concentration of the crack tip of the same size increases and the magnetic memory signal increases.When the wall thickness increases,the stress concentration at the crack tip of the same size decreases and the magnetic memory signal weakens.When the internal pressure of the pipe increases,the magnetic memory signal also increases.As the Angle between crack and circumferential direction increases,the stress Angle decreases and the axial magnetic memory signal at crack tip increases.