考虑磁极边缘效应的管道轴向磁路模型OA

[Objective]The magnetic circuit method is a rapid analytical technique employed for analyzing pipeline magnetic fields and optimizing the design and performance of detection devices.Existing traditional magnetic circuit models based on idealized assumptions often neglect the effects of fringing flux and the nonlinear characteristics of ferromagnetic materials when calculating the internal magnetic field in pipelines.This leads to significant discrepancies between theoretical models and measured results,directly affecting the reliability and accuracy of detection device design.[Methods]To address these issues,this study proposed a magnetic circuit modeling method for pipeline axial magnetization based on magnetic field segmentation,which focused on the practical impact of fringing reluctance to establish a more complete mathematical model of the magnetic circuit.The magnetizing device and the pipeline were treated as a coupled system.According to the distribution path of the fringing magnetic field in the excitation zone,the magnetic field segmentation method was employed to divide the system into cylindrical and spherical subregions.The magnetic permeance expressions for each subregion were derived separately,thus constructing a more accurate mathematical description of the air-gap permeance.Meanwhile,the expression of the pipeline magnetization characteristics was obtained by analyzing the magnetization characteristics of X52 carbon steel.On this basis,an equivalent magnetic reluctance network was introduced to establish an axial magnetic circuit model for pipelines that accounts for fringing effects.The magnetic field intensity in the air gap of the magnetized zone and the distribution of the effective internal magnetic field in the pipeline were calculated.To validate the accuracy of the model,a three-dimensional finite element simulation model of permanent magnet magnetization for pipelines was constructed,and an experimental platform was set up to physically measure the air-gap magnetic field at the excitation end.Finally,based on verification of the effectiveness of the proposed model,a systematic analysis was conducted on the influence mechanism of the structural parameters of permanent magnet magnetization detection devices on the effective magnetic flux inside the pipeline.[Results]Compared with traditional magnetic circuit models,the proposed magnetic circuit model demonstrates higher accuracy in calculating the internal magnetic field of pipelines.The calculation results are in good agreement with finite element simulation results,with the relative error of magnetic field intensity not exceeding 5%.In the experimental verification of the air-gap magnetic field,the error between the calculated values of the improved model and the measured values is less than 30%.This error mainly originates from sensor positioning deviations and material property fluctuations during actual measurements,while the model itself still exhibits strong robustness.Further analysis indicates that the fringing effects of the magnetizing device cause significant attenuation of the effective magnetic flux inside the pipeline,and the leakage flux coefficient is proportional to the effective magnetic path length of the magnetic poles.When the pole spacing is 1.25 times the effective magnetic path length of the poles,the pipeline can be magnetized to saturation while the fringing magnetic field is effectively suppressed.[Conclusions]The proposed axial magnetic circuit model for pipelines considering fringing effects not only deepens the understanding of the internal magnetic field distribution,but also provides important theoretical support and modeling guidance for the structural design of high-precision permanent magnet detection devices.This work is of positive significance for improving the technical level of pipeline nondestructive testing.