Signal Processing Method For Magnetic Flux Leakage Of Complex Surface Components Based On Analog Phase Shifting

MFL(Magnetic flux leakage)nondestructive testing(NDT)is widely applied to product quality inspection or in-service damage detection of ferromagnetic components.The development direction of current MFL NDT is from conventional regular contour objects,such as steel tube / plate to complex contours,such as welding parts,wire rope and thread parts.But in the MFL NDT of the complex surface component,due to the interaction between the magnetic field and the defect leakage magnetic field caused by the complex surface,the signal is very complex,which reduces the detection and recognition ability of the defect signals.First,the background signal produced by the complex surface of ferromagnetic components in MFL NDT conceals the defect signal,resulting in the problem that the defect signal is difficult to detect and identify.In view of this problem,we propose a signal processing method based on multi-channel signal phase-shifting to eliminate or reduce the characteristics of the surface magnetic field so as to improve the recognition degree of defect MFL signals.We analyze the detection characteristics of complex surface components and have put forward the specific plan of signal processing circuit design.Then,on the basis of analyzing the principle of amplifying circuit and phase shifting circuit,the Multisim simulation model of preamplifier circuit and phase shifted circuit is established,determining the parameters of the electronic components in the circuit.A simple phase shift circuit is then set up,we use sine wave verify the accuracy of phase-shifting circuit.And then,according to the simulation analysis of multi-channel signal processing circuit,the signal processing circuit is redesigned.It mainly consists of three modules,the preamplifier circuit,the phase shift circuit and the differential circuit.The selection of electronic components used in the circuit is introduced in detail.The amplification and phase shifting function of signal processing circuit board are further verified by sine wave signal.Finally,the signal processing circuit acquisition module and the panel of MFL NDT system instrument are designed,and the instrument of the MFL NDT system are reproduced.The MFL testing system is used to test the existing wire rope and corrugated plate,which verifies the accuracy and efficiency of the signal processing circuit in the detection system.