Eddy Current Non-destructive Testing System Based On GMR Sensor

With the development of the aerospace industry,large and complex aircraft structures are becoming more and more common,and the demand for non-destructive testing of aircraft aluminum is also increasing.Conventional non-destructive testing methods include ultrasonic testing,radiation testing,magnetic particle testing,penetrat testing,and eddy current testing.Among them,eddy current testing has been highly valued and developed rapidly in the field of non-destructive testing due to its non-contact properties,high sensitivity to detection of surface and near-surface defects,fast response,and digital processing of detection results.The research hotspots of Eddy current array detection technologies include high-performance probe structure and parameter design,development of high-performance eddy current testing system,rapid discrimination of defects and imaging.In this thesis,the probe parameter design and high-performance eddy current testing system are studied.In terms of probe parameter design,the sensitivity of the traditional coil probe decreases with the decrease of the operating frequency,and it has the disadvantages of small detection area and high dependence on automation.Therefore,this thesis designs an eddy current probe that uses a giant magnetoresistive(GMR)sensor instead of the detection coil.The giant magnetoresistive(GMR)sensor can directly detect the magnitude of the eddy current magnetic field,and because its sensitivity is independent of the operating frequency,the probe has high sensitivity even at low frequencies.In this thesis,the equivalent model of the excitation coil and the test specimen depression was established by Maxwell simulation software.The simulation data was used to determine the parameters of the excitation coil and the probe was made in kind.Through simulation,the following conclusions are obtained: The sensitivity of the probe is positively related to the excitation current;the ability of the probe to detect surface defects increases with the increase of the excitation frequency;compared to the defect width,the probe is more sensitive to the depth of the defect.In the eddy current testing system,a set of non-destructive testing system with adjustable excitation signal frequency and amplitude was designed.Using this system for experimental detection,experiments show that the performance of the new probe is consistent with the simulation,and small defects can be effectively detected.