The Research Of Magnetic Flux Leakage Testing Technology Based On Electromagnetic And Permanent Magnet Excitation Method In Series

At present,the magnetizing mode of magnetic flux leakage technology is relatively single.Magnetswithdifferent intensity that correspondsto different thickness ofsteel plateare needed to be designedin permanent magnet flux leakage testing.Electromagnetic excitation creates a great number of heat and its structure is very heavy. It workswith thebasic principles of magnetic fluxleakage testing.The new magnetic flux leakage detection technologybased onthe electromagnetic-permanent magnet excitation methodis to cascade the electromagnetic and permanent magnet. It is a new nondestructive detection technology which is applied to tested ferromagneticmaterials using the composite magnetic source.The composite excitationmethod was used in electromotor before. While, the paper puts forward an application of the excitation method on the plate whose material is Q235in the magnetic flux leakage detection technology. The new magnetic flux leakage detection technology is studied according to these above.The paper describes the electromagnetic-permanent magnetcascading excitation model. In the model, DC coil is wound on the armature, by which the magnetic source that cascadeselectromagneticand permanent magnetis obtained. The magnetic flux leakage testing was conducted on the specificspecimen. In order to verify the validity and effectivenessof this method, simulation analysis of the testing was carried out with the help of ANSYS. Firstly, the composite excitation modelwas established and then air cover was around the model. Through a series of stepsof ANSYS software, such as the line division, meshing, loading boundary conditions and solving, the analysis results were obtained. In the simulation, a series of single variableincluding defect depth and number of ampere-turnswere changed respectively. Then the influence of these factors on the leakage magnetic field distributionwas summarizedafter extractingthe signal of leakage magnetic fieldin x and y direction overthe defect ina distance of1mm respectively.According to the finite element simulation results, the size of magnetization structurewas determined andthen the parts of magnetic flux leakage testing instrument were designed. After machining the magnetic flux leakage testing instrument based on the composite excitation model was assembled using which the experiment was conducted. The experimental results were basically identicalwith finite element analysis results and the theory was verified.