Research On Magnetic Flux Leakage Testing Technology For Surface Defects Based On Open Magnetic Field

The common equipment containers for petrochemical industry are mostly made of ferromagnetic materials.They operate under natural conditions and liquid level changes for many years,so they are inevitably subjected to various damages.Especially the corrosion perforation,crack propagation and cracking caused by the chemical corrosion and electrochemical corrosion in the environment,non-destructive testing and evaluation of defects,is of great significance for reducing accidents and reducing costs.Based on the theory of magnetic flux leakage detection,this paper studies the magnetic flux leakage detection technology based on open magnetic field using open magnetic field detection principle and open magnetic field detection characteristics.This paper uses the combination of theoretical analysis and experimental research,based on the theoretical basis of the open magnetic field of surface defects,the surface defect analysis model is established by using finite element simulation analysis to study the spatial distribution characteristics and influencing factors of open magnetic field of surface defects.Analyze the feasibility of open magnetic field detection of surface defects.In the finite element simulation,by changing the depth and width,the height of the magnetization structure lifted off,the height of the lift height of the sensor,and the crack aspect ratio parameter of the surface crack defect and the cone etch pit defect,the change of magnetic flux density is reflected by different parameter changes.The effect of the spatial distribution of the open magnetic field of surface defects was studied by extracting the features above the defects.Under the condition of the requirements of surface defect detection and open magnetic field detection characteristics,the overall structure of the magnetic flux leakage detector based on open magnetic field is designed,and the configuration of excitation device,data acquisition system,signal processing system and software is determined.Based on the finite element analysis,the overall design scheme of the surface defect magnetic flux leakage detection system based on open magnetic field is developed.The physical instrument is processed,artificially simulated defects are prefabricated under laboratory conditions,different thickness defect detection experiments,corrosion pit defect experiments and surface crack defect experiments were set up.Multiple experiments to reduce the error,collect surface defect detection data,and finally compare the experimental data with the results obtained by finite element analysis,the experimental results obtained are consistent with the finite element simulation results,and the feasibility of the magnetic flux leakage detection technology based on open magnetic field is verified.