Research On Pipeline Stress Detection Technology Based On Electromagnetic Technology

Pipeline transportation is one of the most important transportation modes of international oil and gas,and the safety maintenance of pipeline is the key problem of pipeline operation.The long oil and gas pipeline will produce local stress concentration phenomenon due to internal pressure in the process of use,and stress fatigue crack will be produced under the repeated action of long-term stress,and the crack will expand rapidly under corrosive environment and fluctuating pressure,which has a serious impact on the pipeline transportation safety.Therefore,it is very important to reduce the accident rate through the detection of pipeline stress condition The pipeline stress detection method based on electromagnetic technology,as a developing non-destructive testing technology,has a wide application prospect in the military and civil fields.The existing research lacks a comprehensive analysis of the magnetomechanical relationship,so the establishment of a new magnetomechanical relationship model is of key significance to the application of the theory and practice of detection technology.Based on Jile Atherton(J-A)theory,the magnetoelastic energy density function due to magnetoelastic effect is introduced,and the stress demagnetization term is considered.The magnetomechanical model of pipeline under stress state is established,and the equivalent field strength under the combined action of stress and magnetic field is determined.The analytical solution of stress and magnetization of ferromagnetic material under the condition of non-magnetic saturation is obtained.The distribution law of magnetic signal in stress concentration area of steel plate and pipe crack is analyzed by using ANSYS finite element simulation software.Through the comparison of magnetic signal in stress concentration area with different stress size,the corresponding relationship between different stress and magnetic signal is analyzed,and the stress distribution law of stress concentration area under quenching water cooling is analyzed.The stress detection system was designed,and the experimental platform was set up under laboratory conditions.The tensile test in different detection directions and the simulated pipe pressure test were carried out on the steel plate without residual stress.The relationship between the stress and the detection signal was analyzed through the real-time measurement of the stress value by the detection system.The steel plate was cooled by quenching water,and the single point measurement was carried out for many times The simulation results are in good agreement with the experimental results.The results show that: the eigenvalue of magnetic signal in the stress concentration area of steel plate and pipeline increases with the increase of stress,and there is a linear relationship between the eigenvalue of magnetic signal and the stress value.The stress in the central area of the circular stress concentration area produced by quenching water cooling is larger,and decreases with the increase of radius,but increases again at the edge of the stress concentration area.