Pipeline stress detection based on dual-field stress-magnetic coupling

TIAN Ye; CHEN Haiyan; GAO Fuchao; DING Rong; WANG Guoqing

doi:10.7688/j.issn.1000-1646.2025.05.09

Abstract：[Objective]With the continuous expansion of oil and gas pipeline transportation,the importance of pipeline safety inspection has become increasingly prominent.Stress concentration at pipeline defects is the main cause of crack propagation and fracture accidents.However,existing detection methods struggle to achieve quantitative stress evaluation.[Methods]This study proposed a pipeline stress detection method based on dual-field stress-magnetic coupling.By incorporating changes in the Jiles-Atherton(J-A)model parameters under different pipeline stress states,a magnetic stress detection model was built.The effects of elastic stress,plastic strain,and external magnetic fields on magnetization intensity and magnetic signal characteristics were systematically analyzed.The study was grounded in the principles of magnetic stress detection,the J-A model,and magnetic charge theory.By examining the influence of stress at different stages and external magnetic fields on magnetization intensity and magnetic signals,the relationship between hysteresis loops and magnetization intensity under varying conditions was established.In addition,the variation patterns of axial and radial signals under different stress and magnetic field conditions were identified.A proportional coefficient was introduced to develop a dual-magnetic field stress detection model,and separate models for elastic and plastic stress detection were built.Finally,experiments were conducted to verify the theory.Equivalent magnetic field strength formulas for the elastic stress and plastic strain stages were derived,clarifying the variation laws of the pinning coefficient k,shape coefficient a,and domain wall coupling coefficient α with stress.Experimental validation was conducted using X80 pipeline steel specimens subjected to tensile loads ranging from 10 to 80 kN and external magnetic fields from 0 to 10 A/m,with magnetic signal characteristics measured.[Results]The axial component of magnetic signals under different magnetic fields and stress levels exhibits distinct peaks,with peak positions remaining stable despite variations in external fields or stress.Tangential peaks increase with the external magnetic field,aligning with theoretical calculations.Experimental data indicate that the model closely matches measured results under high stress,with minimal error,while low-stress scenarios show slight deviations due to parameter fitting limitations.[Conclusion]In the elastic stage,tensile stress causes the hysteresis loop to rotate counterclockwise initially and then clockwise.Magnetization changes significantly under weak magnetic fields,whereas stress effects become negligible under strong fields.During the plastic stage,plastic strain reduces the slope of the magnetization curve,and both the initial magnetization curve and hysteresis loop rotate clockwise.Magnetization intensity is proportional to magnetic signals,with the ratio of strong magnetic signals to magnetization intensity serving as a proportionality coefficient dependent solely on defect size.The dual-magnetic field stress detection model demonstrates high accuracy under high stress,confirming its capability for stress detection.This study innovatively integrates the dual-magnetic field method with J-A theory,proposing a proportional coefficient-based model for separating elastic and plastic stresses.The approach resolves the issue of overlapping defect and stress signals in traditional methods,providing a high-precision,quantifiable technical solution for stress detection at pipeline defects.This advancement holds significant value for preventing pipeline failures and ensuring safe energy transportation.