Research On Corrosion Defect Detection Of Storage Tank Steel Plate Based On MFL Multi-dimensional Component

In the process of using steel storage tank,the safety problem of tank equipment has been paid more and more attention.Corrosion is a major cause of safety accidents,so it is necessary to detect the corrosion of steel plate.The subject comes from the development of Tuowei(Ruicheng)Co.Ltd.In order to obtain more comprehensive information on corrosion defects,and multi-dimensional evaluation of corrosion defects can be achieved,this article mainly studies the theoretical analysis of magnetic loop of MFL and structure of detecting vehicle,the embedded detection system for corrosion defects and magnetic field strength data analyzing and processing method.(1)Theoretical analysis of magnetic loop and structure of detecting vehicle:Based on the principle of MFL,equivalenting static Magnetic Circuit to DC Circuit.By using Kirchhoff equation of DC Circuit and basic equation of static Magnetic Circuit,the magnetic field intensity BT,which can make the measured steel plate magnetized to near saturation,is derived.The length?width?thickness of permanent magnet is 20mm?80mm?40mm,and the material is NdFeB-N45;Yoke iron material is Q235,thickness 5mm;Steel plate material is Q235,thickness 10mm;The magnetization gap is 5 mm.By inserting the above parameters into BT,1.42T is obtained,which is larger than the theoretical magnetic field intensity of 1.36T,and the near-saturation magnetization of the steel plate is realized.The permanent magnet fixing device,the permanent magnet distance adjusting device and the detecting probe lifting value adjusting device are designed in the structure of the inspection trolley.(2)Calibration of New Magnetic Field Sensor:The stability and sensitivity of the TLV493D-AIB6 magnetic field sensor are calibrated on an experimental platform.Amplitude of variation in direction of X?Y?Z is 0.4mT?0.3mT?0.5mT from TLV493D-A1B6 magnetic field sensor detection;in the magnetic field environment,each move of the TLV493D-A1B6 magnetic sensor probe 2mm,The rate of change of the detected magnetic field intensity data is between 10%and 20%.TLV493D-A1B6 magnetic field sensor has high sensitivity and stability.(3)Embedded Detection system:An embedded detection system for corrosion defects based on I2 C bus is designed,including hardware circuit design and firmware program development,and the 3D acquisition,display and storage of magnetic field leakage intensity data are realized.First,the overall scheme of embedded detection system is developed,and the core components are selected.The hardware circuit is designed,including the smallest system circuit of STM32 microcontroller,the interface and addressing circuit of three dimensional magnetic field sensor(TLV493D-A1B6),DGUS display circuit,SD card storage circuit,and so on.According to each module circuit,it developed some programes,such as 3D magnetic field sensor addressing program,DGUS screen data display program,double extremum filter program and SD card data storage program,etc.(4)Analysis method of Magnetic leakage Field intensity data:By studying the graphical characteristics of Y-direction data and X-direction data of magnetic leakage intensity,the size evaluation of corrosion defects in the magnetization direction and the depth in the unmagnetized direction is realized.In order to study the relationship between the intensity of X direction magnetic field leakage and the depth of corrosion defect,the intensity data of X direction magnetic field leakage were fitted by cubic Fourier series,and seven graphical features,such as center of gravity,length and area,were extracted from the fitted curve.Because the relationship between the characteristic quantity of X-ray data curve and the depth of corrosion defect is uncertain,the artificial neural network analysis theory is used to predict the depth of corrosion defect and the prediction is accurate.