Research On Algorithm Of Quantitative Detection To Magnetic Flux Leakage Of Wire Rope

Due to the advantages of wire rope, it is widely used in many fields such asharbor, elevator and mine hoisting. As service time of wire rope goes on, wireropes will inevitably suffer damage such as fatigue, corrosion, broken wire andwear. Unless the health status of wire rope can be assessed timely and precisely,accidents of broken ropes can not be avoided, which will make huge economicloss, loss of life and personal injury. The ultimate goal of wire ropenondestructive inspection is to find out the distribution and size of the defects forassessing the carrying capacity of the wire rope, so that replacement date of thewire rope could be determined in advance. The premise of this goal is theaccurate localization of defects and the quantitative sizing of defects. In order toimprove the accuracy of the wire rope defect localization and quantitativerecognition, the following aspects of theoretical research and engineeringpractice are carried out in this dissertation.Distribution characteristics of magnetic flux leakage is firstly analyzedbased on the magnetic dipole model. The influence of defects parameters tomagnetic flux leakage distribution is analyzed to obtain the impact formulasbetween the defects parameters and magnetic flux leakage distribution. And themain influencing parameters of the leakage magnetic field intensity distributionis analyzed by the finite element method. A platform based on Hall sensor arrayis established to detect two dimensional magnetic flux leakage of wire ropedefects. Axial and circumferential distribution of magnetic flux leakage areobtained with the developed system, which establish the foundation forlocalization and quantitative detection to defects.The cubic spline method is used to interpolate the magnetic flux leakagedata along the circumferential direction, and the circumferential resolution of theraw magnetic flux leakage image is improved. The contrast of the defectiveregion in the magnetic flux leakage image is improved with cross gradientoperator. A defect localization with local binary pattern is proposed for accuratelocalization both in the axial and the circumferential direction.For magnetic flux leakage signal of experimental steel bars defects, the excitation magnetic field is simulated by ANSYS. According to the basicformulas of the second chapter, the distribution of the magnetic field strength iscalculated. Compared with the measured data, the defect parametersanti-algorithm is put forward. The geometric parameters of the defect iscalculated based on the measured magnetic field data.Discussing the rope MFL signal data transmission system, FPGA controlsection, DSP control section and USB control section is analyzed separately, andthe steps is given. Testing the time of the experimental platform data acquisitionand transmission, the detection rate of wire rope inspection system is evaluated.The detection rate is assessed, which provides an effective foundation for thedesign of real-time online testing.