Detection method for steel structural columns based on magnetically induced electromotive force considering magnetic field angle

HE Liansheng; CHEN Meng

doi:10.7688/j.issn.1000-1646.2026.01.14

Abstract：[Objective]The stress state of steel components is a key parameter for assessing the safety and health of steel structures during long-term service.Existing stress detection methods based on the magnetically induced electromotive force effect do not consider the influence of the magnetic field direction,and variations in the magnetic field angles reduce the accuracy of detection results.Therefore,this study quantitatively investigates the influence of the magnetic field angle on the relationship between stress and magnetically induced electromotive force in steel structural columns through theoretical analysis and experimental research.[Methods]Axial compression tests on short Q235B H-shaped steel column specimens were designed.A manganese-zinc ferrite U-shaped electromagnetic sensor was fixed at the center of the steel flange,and its orientation was varied.During the graded loading process,magnetically induced electromotive force signals at different stress levels and magnetic field angles were collected simultaneously.All tests were repeated twice to ensure data reproducibility.Based on the experimental data,magnetically induced electromotive force-stress relationship curves at different magnetic field angles were established.The specific influence of magnetic field angle on this relationship was examined,and the quantitative relationship among magnetically induced electromotive force,stress,and magnetic field angle was clarified.In addition,the mean gradient of the magnetically induced electromotive force was used to quantify the effect of magnetic field angle on the electromotive force-stress relationship.[Results]Within the elastic range,the magnetically induced electromotive force shows a significant linear negative correlation with compressive stress.The slope of the relationship curve changes markedly with increasing magnetic field angle.The signal sensitivity is the highest when the magnetic field direction is parallel to the principal compressive stress direction.As the magnetic field angle increases,the sensitivity decreases nonlinearly and reaches its minimum value when the magnetic field direction is perpendicular to the stress direction.The characteristic curves corresponding to different angles do not intersect.Under different magnetic field angles,the gradient of the magnetically induced electromotive force tends toward a constant value with increasing stress,and its mean value decreases as the deviation angle between the magnetic field direction and the loading direction increases.[Conclusions]The magnetic field angle affects the accuracy of stress detection.The mathematical expression for the relationship between magnetically induced electromotive force and stress established based on the experimental results shows a good fit.Furthermore,the mean gradient of the magnetically induced electromotive force follows a cosine-function relationship with the magnetic field angle.