Research On Orthogonal Axial Magnetization Eddy Current Probe Testing Method For Weld Defect Detection

Steel materials have a wide range of applications in nuclear power generation,oil and gas pipeline transportation,machinery manufacturing,and transportation,among which steel plate specimens occupy a large part.The steel plate is used in pressure-bearing equipment and other devices,which are mostly used for welding.Under long-term high temperature,high pressure,corrosion and other harsh working environments,steel welds often produce defects such as cracks,corrosion,small holes,etc.Leading to premature damage to the equipment,causing great harm to the economy and the life safety of workers.In order to eliminate this invisible hazard,regular inspections of the steel plate weld area are indispensable.Traditional eddy current probes detect steel weld defects.Due to the different geometric shapes of the welds and the uneven surface,the high magnetic permeability of the steel plate causes the lift-off effect and the skin effect,which reduces the detection signal-to-noise ratio and affects Detection accuracy.Therefore,in view of the above problems,this thesis designs a new type of orthogonal axial magnetization eddy current probe through theoretical simulation and experimental research and establishes a weld defect detection method based on the probe.The main research contents are as follows:First of all,a new type of orthogonal axial eddy current probe is designed on the basis of traditional eddy current testing,and the structure model of the probe is established and theoretically simulated and analyzed using COMSOL Multiphysics finite element simulation software.The simulation results show that the orthogonal axial probe has the characteristics of auto-zero,self-differential,and noise suppression,which can effectively suppress the lift-off effect caused by the uneven surface of the weld.In order to further improve the detection sensitivity of the probe,the simulation software was used to optimize the parameters affecting the sensitivity of the probe,and the influence of the length and width of the probe detection coil and the scanning angle of the probe on the sensitivity of the probe was studied.The probe's sensitivity was determined according to the simulation results.Optimal size parameters and scanning methods,and obtain the best sensitivity probe structure.Secondly,the corresponding probes were prepared and the experimental platform was built,and the sensitivity comparison experiments and the welding seam lift-off effect detection experiments were carried out on the probes.The experimental results show that the probe designed in this paper can effectively suppress the lift-off effect caused by the uneven surface of the weld.Under different lift-off values,the probe can effectively detect cracks with a minimum width of 0.15 mm on the surface of the steel plate weld.Defects,and the sensitivity of the probe is high;at a lift-off value of2 mm,the signal-to-noise ratio of the probe to detect cracks on the weld surface can reach 13.2%,and the effect is better.The research results provide a theoretical basis for the detection of deep defects in steel plate welds.Finally,a theoretical simulation study was carried out on the orthogonal axial probe combined with the permanent magnet magnetization method,and the orthogonal axial magnetization eddy current probe was optimized and the steel plate weld deep defect detection system was built.Use the optimized probe to detect deep defects in steel plate welds.The experimental results show that: in the process of detecting deep defects in the weld,the probe can detect internal cracks with a depth of3 mm and a width of 0.5 mm under the magnetization of the permanent magnet and a lift-off height of 1 mm,and the sensitivity of the probe is better.The noise ratio can reach 19.6%,the effect is better.It laid the foundation for the formation of the automatic detection method for the deep defect of the steel plate weld and the development of the equipment.