Study On Sweeping Pulse Eddy Current Detection Of Laser Cladding Remanufacturing Parts

Remanufacturing technology is a green manufacturing method which can repair or even improve the quality and performance of parts without changing the shape and performance of parts.In this paper,the defects under the cladding layer of laser cladding remanufactured parts are detected.Usually,laser cladding remanufactured parts have the characteristics of complex service conditions and various damage forms.It is difficult to detect and evaluate internal defects,which seriously limits the development of laser cladding remanufacturing technology.The destructive testing method can only sample the remanufactured parts,and cannot guarantee the safety performance of all parts.Therefore,the non-destructive testing method has become an effective method for comprehensive evaluation of remanufactured parts.Common non-destructive testing methods include ray detection,eddy current detection,ultrasonic detection,metal magnetic memory detection,etc.,but each method has some limitations.In order to meet the inspection requirements of laser cladding remanufactured parts,a novel Sweep Pulse Eddy Current Detection?SPECD?method is proposed in this paper to realize the non-destructive detection of internal defects of remanufactured parts.SPECD testing technology is an extension of pulse eddy current testing technology.It uses continuously changing frequency pulse as excitation signal to realize comprehensive evaluation of internal defect information of remanufactured parts.In this paper,the research status of pulse eddy current testing technology at home and abroad is described in detail.On this basis,the SPECD testing theory is introduced and summarized.The response signal is processed by the differential processing method,and the variation curve of the differential response signal is obtained.The eigenvalues are extracted to realize the quantitative evaluation of the defect information.In addition,using COMSOL Multiphysics simulation software,the simulation analysis model of SPECD system is established,and he distribution of induced eddy current and magnetic field in aluminum alloy under sweeping pulse excitation is obtained:the larger the frequency of excitation signal,the more concentrated the distribution of internal magnetic field,the greater the magnetic field intensity,the shallower the penetration depth of induced eddy current,which is conducive to the detection of small defects on the surface of the specimen.The simulation results verify the feasibility and rationality of SPECD technology.In this paper,a SPECD platform is designed and built.It is determined that the probe module of the detection platform is mainly composed of TMR magnetic sensor,ferrite core and rectangular excitation coil.The parameters of inner diameter,height,thickness and turns of the coil are optimized by simulation.The parameters of the excitation coil are determined as follows:inner diameter of the coil is a×b=200mm×10mm,coil height h=15mm,coil thickness T=3mm,coil turns N_p=300 turns,and the diameter of enameled copper wire is D=0.4mm.In order to realize the automatic scanning detection of the detection platform,a two-axis electronically controlled motion platform is designed and built to realize Z-shaped automatic scanning.Finally,the software program of SPECD testing platform is introduced briefly.Using the self-made SPECD testing platform to test the thickness-thinning defect block,the influence of sweep pulse excitation parameters on the detection was explored,and finally the excitation signal parameters were determined as follows:the amplitude of the excitation signal U_ac=2V,the duty cycle of each frequency band T_on/T_T=50%,and the sweep frequency range 50Hz?f?200Hz.Under the action of the above excitation signal,sweep pulse eddy current was used to detect the matrix material.The test results were as follows:the peak value of the signal increased with the increase of the corrosion diameter,and the growth trend showed a S-shaped curve change law of first increasing and then decreasing.Under the same corrosion defect,the peak value increases with the increase of frequency band;the signal peak value increases with the increase of crack depth,the growth trend slows down,and the starting point moves forward with the increase of frequency band.The peak value of the signal at the same crack increases with the frequency of the excitation signal.When the depth exceeds 6mm,the peak value of the signal tends to be constant.The peak value of the signal increases exponentially with the increase of the thickness.The peak value at the same thickness defect increases first and then decreases with the increase of frequency band of excitation signal.Lastly,the SPECD testing of laser cladding specimens was carried out to determine whether the prefabricated defects of the specimen matrix were completely repaired,and the defects that could not be completely repaired were quantitatively detected.